• GE Profile PEM31xxxx (1.1 cu ft).
• Sharp R12xxxx
• Whirlpool WMT50011KS (must be built in)

Great, list, thank you! Sadly, I guess I'm currently in the market for something in between the 2 GE microwaves. I shouldn't go any bigger than 12 1/8 H x 24 W x 12 7/8 D, but was hoping there was something with more capacity than 0.7 cu ft (maybe in the 0.9 cu ft range). I take it I can't just use any old countertop microwave, right? I'm surprise at how few options there are to do this. If anyone knows of anything in between the two GE sizes, I'd love to hear! Otherwise I'll have to decide between the two of them...either slightly too large or slightly too small...

Yes, you can use any tabletop model, as long as there is enough space around the unit for air circulation. We purchased the largest GE model, and our GC installed it on a shelf above the counter. 6 years, no issues. We keep the Breville toaster oven underneath.

How far does the microwave stick out please? Figure that out first or you may have to notch the adjacent doors.

The microwave won't stick out at all. We're putting it under a diagonal corner cabinet so it will fit underneath the cabinets, but that does give us limitations on width and depth. I think the larger GE will fit, but something a bit smaller (but not as smaller as the smaller GE) would be better.

In terms of circulation, there will be enough space underneath and in the back and sides, but obviously no circulation above the microwave, which is why I was wondering if a countertop model will work (because maybe they vent out the top?)...

"I shouldn't go any bigger than 12 1/8 H x 24 W x 12 7/8 D, but was hoping there was something with more capacity than 0.7 cu ft (maybe in the 0.9 cu ft range)."

Don't worry about the oven capacity. Instead consider the dimensions of the cavity and how you'll use the oven. The PEM31 has a 17-3/8W x 9H x 12-1/4D cavity while the JEM3072 has a 12-1/4W x 7-7/8H x 11-5/8D cavity. If you need a microwave with a cavity is sized for a large dinner plate, get the JEM3072. Otherwise, get the PEM31 whose turntable can be turned off to accommodate a wider dish.

• Contoure RV-787S-UCKIT 0.7 Cu. Ft. Stainless Steel RV Microwave with Under-the-Cabinet Kit