Thank you everyone! Encouraged by your replies, I started with looking at meangoose's link and renewed my search. I stumbled across a Frigidaire FGGC3045KB on a big L box store's site that was on sale for about 40% of the original $899 MSRP (still available at a huge savings if you add it to your cart to view the price). It has a 17,000 and a 12,000 burner. Although they are front burners, I am happy to get such high BTU at a savings. It has continuous grates and I was able to get the black that I preferred. I was actually able to get it for even less through price matching at a local retailer who will install it next week. Hubby was so happy that he went to the store and ordered it himself! I am confidant that jumping from 9000 to 17,000 will speed up my boiling significantly. Maybe I will even get adventurous and make a great stir fry!

What models are you looking at? It is hard to say if there would be much difference. It depends on how the burner is engineered and the type and size of pan. Some sealed burners have more flare than others. If you have a pan that is smaller in diameter, like a narrow stockpot, you may lose more heat around the pan if it has more flare on the highest settings. I would most likely consider other things besides the high end of output of one burner. What are the outputs of the other burners? What is the low end of the burners in BTUs? Phrasing such as "very low simmer" or even a given temperature do not mean much and are highly subjective. How much play is in the knob and how does it move through the range of heat? Does it suddenly go from low to high or is there fine adjustment? How will the cooktop be to clean? What are the grates made of? Do you like the placement of the different sizes of burners?

I'd like to offer a little different opinion. It's been awhile since I've posted to the forum here, but I've actually commented on this very issue before. Three years ago, I got the Kenmore Elite all gas, with 5 burners, the lowest being the 5000 BTU. It seems like the general feeling is that this is worthy only of being called a "warming" burner. Having been completely enthralled with getting back into gas cooking (not since college), I also liked having different sizes of burners. I read that the flames on a 5000 burner are just as hot as the flames on a 17000 burner. The difference is just that there is alot more flame! I have experimented quite a bit. I've found the 5000 burner is the perfect size with most 2 qt sauce pans. I like this size for boiling sauce pans full of water to hard boil eggs. I like it for heating food in stainless sauce pans. I also have (just to try) cooked food in a 10" cast iron skillet over the 5000 burner. It took longer than over a 9500 (or 14200, or 16200), but it worked. Obviously, it takes a little while longer. But the size of the flame is perfect for most 2 qt pans, and I've found that heating up some leftovers in a 2 qt stainless sauce pan works so good over the 5000 burner that I now prefer this to using my microwave. I hope this is helpful.

I'll try to help, but my answer will be roundabout. We have a gas direct vent insert in our living room. I've forgotten the numbers, but the BTU rating and related square footage of space it would heat was nearly equal to our whole house, which is a one-story 1550 square footer. I didn't pay much attention to those numbers. I just wanted a nice warm fire in the living room for our own enjoyment, but also to provide emergency heat when an ice storm causes a power failure. Our fireplace gives us a very nice warm fire, and it probably could warm nearly the whole house IF it were connected to some kind of ductwork that would circulate the heated air to different rooms. We do not have such a duct system. What happens with our unit when it is on for more than, say, 10 minutes or so, it gets really hot, almost like what I imagine a blast furnace feels like. The way we deal with that is with a remote control thermostat. It really works. After some trial and error on the temperature setting and on where you put the thermostat, you can zero in on the optimal arrangement. Then the thermostat turns off the fire when the desired setting is reached, and turns it back on when the temperature drops below the setting on the thermostat. Most of the direct vent inserts and fireplaces come with thermostats as an option at an extra cost. They charge too much for them, but I think they are worth getting. Otherwise, you'll wind up turning the system on and off manually, and that gets to be a nuisance. One other point: Some or all inserts and fireplaces come with a blower that draws air in from under the firebox, then up around the back of the firebox where it gets heated, and then blows the heated air through openings just above the firebox. These blowers serve to distribute the heat a bit more effectively than you can get with just the fire alone. We rarely use ours. At high speed, it's too noisy, and at low speed it makes an annoying rattling sound that we don't like. Another option for distributing heated air is with a ceiling fan that moves air the opposite direction of during the summer -- it draws air up instead of down. This creates a gentle draft that can move heated air to areas in the room that might not otherwise get heated. But you can only use such a fan if you have a direct vent system, because such a system is sealed and does not depend on the updraft in a conventional fireplace. I hope this info helps you in sorting out your options. Good luck