If you look at the Modern-Aire site, they have several shapes where the front tapers at the top to the depth of an upper cabinet, and the sides are straight so as to butt up to, and cover, the yellow cabinet sides you mentioned. Their typical sizes are 18" and 30" high, but you could get a 24" custom one if your budget allows. Or you could get an 18" and have a box made for above it to cover that area and to which you could attach replacement moulding. The box could be made of either wood matching your moulding or sheetrock. Vent-a-hood has a stainless direct replacement if you decide to stick with the same size you now have. I'm attaching the link to the Modern-Aire page that shows their shapes. PS-10, PS-11, and PS-26 all have the characteristics I was talking about above. Here is a link that might be useful: Modern-Aire Hoods

Rereading this thread in its entirety -- a trip down memory lane -- reminded me of some web sites with filters on their search function such that when one clicks on enough constraints there are no candidates left to purchase. feisty68's constraints have a similar effect. Thinking that maybe there is some way out of the box, two concepts come to mind to bring up: (a) One can choose a hood with internal blowers (as seemingly required) that has more specified flow than the external duct can handle. In this case, at full power the flow will be low, (or possibly zero, depending on the fan curve shape), but when run at part power to yield an appropriate flow rate for the duct, there should be reasonable flow. Whether this is adequate flow would require some analysis. At partial power the blade tip speed will be less and lower noise should result. For example, a VaH hood with two motor squirrel cage fan assemblies run at part power would likely still expel grease onto their housings as intended. Choked flow, however, may be sooner (CFM-wise) than a similar over-sized conventional blower / baffle system due to the nature of a squirrel-cage blower (as implied by VaH CFM vs. pressure loss data). I wouldn't want to guess which approach was louder at the power setting that was at the point of diminishing returns, CFM-wise. Related to this category is using an inline axial blower designed for higher pressure loss at the desired actual flow rate. Fantech might help here. Such blowers may be noisier, so an in-line silencer on the hood side of the blower might be essential. There are screaming-mimi aerospace fans that can push 1600 CFM through a six-inch duct. (b) The other concept is a hybrid exterior/recirculating hood scheme. I think both Best and VaH have examples of recirculating hoods. In this concept, if the actual systems are so configurable, the path to the filter pack would be split with one branch going outside. When the pressure losses of the exterior duct path rose high enough as blower power increased during heavy cooking, additional flow would be through the filter pack and back into the room. Some recirculating hood users here have commented on effectiveness and noise and their threads might be discovered and checked for relevance. Obviously, the simpler approach here is recirculating without engaging the external ducting. In that case, a separate soffit blower, soffit face register scheme could be used for further kitchen overall ventilation, helpful (slowly) when the oven is opened. kas

On the second half of your question, almost everyone here will tell you NO and I would agree. Most don’t even vent, they just recirculate. On the the first part, there are experts here better qualified than me, but there is a significant difference between 200 cfm and 400 cfm. Unless you have a non-standard duct, I don’t see a problem going higher. Hopefully others will chime in. Good luck!

Expanding on what emho23 and jhmarie said, it is helpful to bear in mind that there's a difference between "the best possible," "optimum" and just "okay" (a/k/a what emho called "fine" or what I have called "acceptable compromises for the budget, design and circumstances.") Emho mentions wrestling with the issues. Many of us have wrestled with the resolving of choices of appliance compromises. At some point, we all wind up spinning and thinking "why is this so hard?" And if you think choosing a hood is hard, wait til you get to choosing a washing machine! LOL. So, let's try sorting through your preferences to see if we can make this a little easier for you to figure out. First, let's clarify what you meant when you said you "didn't realize all the $300-1000 ones in the big box stores were all recirculating or weren't a complete package." Are you thinking most are recirculating because the product tagline descriptions on the big box store websites rarely say a hood is "ducted?" The key here may be in knowing that almost all hoods at the big box stores will vent to the exterior by default but can be switched over to ductless. IME, the tagline descriptions in the product listings that say "ducted" or "ductless" are used only for the models that can't be switched from one mode to the other. If the tagline doesn't say one of the other, the hood is one you can vent to the exterior. Does this clarification maybe open up a wider range of choices for you? Second, you say you want a focal point hood on a wall between two windows. So, I'm thinking, maybe what you have in mind is a wall space without cabinets where you are looking for a pyramidal-shaped, wall mounted, canopy style of hood with a kind of chimney rising from the top of the hood. A hood with a canopy is a good thing because the canopy (as opposed to a flat base) is big assist in capturing the rising plumes of steam, heat and vaporized cooking effluents. A flat base can be acceptable if you have to do that route (as I did) but a canopy is better. With a good canopy, there is less concern with large numbers in the fan CFM ratings. As Kaseki has often explained here before (in excellent technical detail for those who want it), capture area is as important to hood efficiency as the fan power, and often more so. That likely gives you a much wider array of choices of hoods. Third, emho mentioned getting a 36" wide hood for the Jenn Air version of your Kitchenaid range. That reflects a standard recommendation here. The extra width enhances the hood's ability to capture cooking effluents (steam, aerosolized grease, etc.) which rise in an expanding cone. That brings us to the compromise in most less expensive hoods. Many are only 19" or 20" deep, front to back. Put a big pot of pasta water to boil on a big front burner on your stove and maybe some steam gets by the front of the hood. Neither the best nor the optimum design, but maybe okay for everyday living and cooking? Fourth, your builder's reluctance to install a vented hood in your kitchen might be understandable if the new house will be very tight, as many newly built homes may be. In that case, adding an unplanned-for hood may pose regulatory and practical problems. If your jurisdiction has adopted International Residential Code Section M1503.4 and/or International Mechanical Code Section 505.2, you might be able to avoid regulatory issues by simply choosing a hood with fans rated at 400 CFM or less But, there is still basic physics to deal with when the new house will be very tight. While you might avoid those kind of regulatory issues by choosing a hood rated at 400 CFM or less, and/or putting it in yourselves as DIY project, you've still got to look at the practical concerns. The biggest practical concern is one of safety. This concern arises when there are fireplaces or gas appliances from which CO can be backdrafted regardless of whether your range hood is rated below 400 CFM. You might avoid the CO backdrafting concerns if there are no fireplaces or wood-burning stoves and if the heating appliances have their own powered air intakes and exhausts sealed off from the rest of the house. However, a tight house still poses a practical physics problem akin to sucking air out of a closed box. (For that matter, I've seen a house so tight that the even bathroom fans didn't work well.) Where things can get really complicated (and therefore) expensive is when you have sought something like a LEED certification, or your builder is trying to meet the performance-based standards of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (e.g., ASHRAE ¶ 62.2), or the house is built in a state with it's own performance-based interior air quality standards such as those that Minnesota, Wisconsin and California have adopted. That means expenses for measurements and testing and maybe MUA expenses before adding an unplanned range hood to the design. OTOH, the builder may just be looking for a way to avoid dealing with the problem so as to move on to the next project. Or, maybe, all of the above.