What is behind the downdraft? I have the KA and selected it because the motor can be switched to the backside of the unit. I did this to allow for full depth drawers underneath. I have a odd shaped island (like a quarter of a pie with 2 long sides connected by an arch) and we had dead space back there anyway.

I can't offer any help with the induction question. But I do have the Dacor REMP downdraft with remote blower at 600 CFM. Our Dacor cooktop is on an island and I didn't want an overhead hood. This downdraft works so much better than my previous Thermador. We're very pleased. We've had it for 4 years and it works great. Check the installation instructions to verify the length of your ductwork and the number of bends to make sure the volume is sufficient for you needs. Dacor also makes a 1000 CFM but it's really quite large. Our duct vents through the crawlspace and we didn't have room outside the house for the larger unit. We would have needed to excavate the dirt about 18" to make room. But our 600 CFM works well for us.

In theory. I'd check the specs and installation instructions of the Thermador to make sure it would fit into the space and would line up with the existing vent pipe.

I realize downdraft vents engender much heated debate about whether the work effectively or not. Let's say I have no choice and need to install one. Which blower system takes up the least space in the cabinet beneath? We can't remote vent or install in crawlspace underneath kitchen. I really like the Best Cattura but its Flex blower essentially takes up an entire base cabinet. Would Jenn-Air or Dacor have more compact blower systems? We're installing in an island, venting a 36" Bertazzoni gas cooktop (and we don't fry, wok, etc much at all), 24" standard base cabinet with 12" empty cabinet behind it. Thanks for the advice!