I have had the Kitchen Aid KEMS308S for 5 years. I had not noticed that the microwave power was low. I doubt that power will be an issue. I assume that many ovens have cool down features. They are not running when the door is open. It is ture that the fan makes some noise, but it isn't that noticable. When I originally purchased this oven I had been intending to get individual ovens, but it turned out that the individual ovens had been discontinued. I see no difference between your choices because they are all double ovens and when one fails, they both fail wheras individual ovens could be replaced individually. I have not heard of the microwave section showing a high rate of failure. You didn't even mention the advantage of the micro/convection. It is not just a microwave, but a real convection oven with a broiling (sort of) element. It is not a speed oven because it does not microwave and heat at the same time. Actually it CAN microwave and crisp via the broil element. Anyway it is a small second oven that can bake a pie or bread (or a small trey of cookies I suppose). It heats far faster than the regular large convection oven because it is small. I find it very useful. The only problem is it is occasionally in use when I would want to reheat a cup of coffee etc. I keep an old microwave in the garage for those cases. While I hope I have relieved your concerns, I believe that there IS an issue. I have had no problem with my oven, and it has been several years since the Main contingent of problems: similar models have encountered a higher than normal thermal fuse blowing during the large oven self cleaning cycle. Unfortunately, the fuse is located on the back of the oven and is a $50 item and shuts everything down. Of course, most people see no problem (myself included) and the problem is certainly due to excessive heat behind the cabinet that could probably relieved by making sure that there is a little more open space back there since you are still installing cabinets? In any case, this is probably a general issue. Other ovens have failed on self clean cycles. At this point, many people concider the self clean to be a marketing ploy and don't use it. Perhaps we just don't make enough spattering roasts, but I have easily wiped down the main oven. It wasn't stuck on hard. Perhaps the surface has anti stick coating? My self cleans have been done mainly to test the thermal fuse problem. By the way, the microwave interior is stainless steel and IS much harder to clean. In fact, that last sentence is probably my most important piece of information. I imagine it would apply to other convection microwaves.

I agree with Jpmom that you don't want a MW on top of a double oven - it's just too high. However, although she does not like a MW drawer, many people on this forum adore theirs (note that all MW drawers are made by Sharp, so if you decide to get one, no need to pay up for a different brand name, as it is just a rebadge). Is there no other location in your kitchen? Do you have a pantry where you could keep the MW? There was just a recent thread on this MW placement topic. http://ths.gardenweb.com/discussions/3833699/placement-of-a-microwave?n=42 I am not a fan of the oven/microwave combos, as I think there are too many compromises in both in order to combine them. Just MHO. If you are doing a major kitchen remodel, you might want to re-think the cooktop in the island, mostly because how are you going to exhaust it. This topic has been covered a zillion times on this forum, but the upshot is if you care about good exhaust, you should have your cooktop on a wall, so that the exhaust capabilities are not hampered by trying to exhaust over an island setup. On the other hand, many people are absolutely fine with poor or no exhaust, and perhaps that is you, so never mind.

Bosch ovens are quite reliable. I recently remodeled and installed the Bosch Benchmark side opening oven with a Sharp microwave drawer under the oven. I had to upgrade my electrical panel as current Code required that each major appliance be on its own heavy duty circuit and I went from a stove to wall oven, microwave drawer, hood, dishwasher and refrigerator. My remodel required a new electrical panel which was costly but not as expensive as it might have been. As The Cook's Kitchen posted, the actual cost would depend on the distance from the main source as well as difficulty in running new wiring. I live in a high rise and was lucky because I was relatively close to the "source". My next door neighbor was not that lucky since he was too far from the main source and so his new panel required a much more costly installation. My advice is that before you make such a limited choice, you get an electrician to determine what would need to be done and what it would cost. While no one is glad to spend money - especially on inside the walls kinds of things :-) - my kitchen electricity was really substandard and not up to Code as it had been installed in 1965. My old outlets weren't GFCI and I couldn't run the counter microwave at the same time as the toaster :-). I also gain peace of mind as God knows what the electrical connections for the old Caloric electric stove were :-).

My daughter did what you are planning on doing. I’m not sure her gap was exactly the same size and her ovens were only 24” wide. Since she did not want to remodel her whole kitchen, she stuck with 24” wide replacements. She put the oven on the bottom and used a speed oven/microwave on top. Like hers your microwave will need a shelf to support it. She had a carpenter put in a shelf and a filler piece between the lower oven and the upper. She also needed an electrician to put in an outlet for the microwave/speed oven. Her over the cooktop microwave was replaced with a vent hood Good luck with your project.