If I'm not listening at reference levels, at least very often he-he-he Is it OK to stack two 2200's on top of a 7500? If I'm using a 990 can I stack two 2200's on the 990?
Thanks

I wouldn't stack anything on top of a class AB amp like the 7500 - that top plate is swiss cheese for a reason, and it likes to have unobstructed air flow off that mass of heat sinks. The 990 is less critical, but there's still a patch of air vents near the back that I'd want to keep clear. My SMS-1 is stacked on top of my 990, but it's only about 6" deep so the vents are comfortably clear of obstructions. The 2200 is closer to 12" deep, so I'm not sure if they'd conflict with the 990's vents. If you can, try to leave the tops of both the 7500 and 990 clear (definitively the 7500). If you simply must stack the 2200's on top of the 990, try to leave plenty of breathing room above the 2200's and behind the entire pile - and it wouldn't hurt to pick up a cheap indoor/outdoor digital thermometer and use the outdoor sensor to track the temperature on top of the 990 (perhaps on a little paper-clip or matchbox stand) to see if it's getting too hot back there.

I agree with Gonk. That's just not a good idea at all. If you absolutely MUST stack those 2200's on top of the 7500, put something under the 2200 feet so you've got some daylight between the components. 6-8 poker chips stacked under each foot, should buy you enough clearance to avoid the china syndrome....ok...ok...a thermal shutdown. :-)