Its looking like I might be upgrading from a receiver to separates but it might be a bit tight on my rack.

Can someone tell me the minimum overhead clearance for both the 7500 and 7700. I've always used 5" as a rule of thumb but have never owned such a beast before. My rack is open only at the front but has good clearance on the sides and back.

I ran my old Model 750 in an open rack (just sides, no obstruction front or back) with just over 1" clear above it. That's less than I recommend (call it a case of "do as I say, not as I do" ), but the air space above the 750 never got much above 100F even in the summer. I've got about a foot above my 7500 right now, but it's also in a closed cabinet. Ideally, I'd try to have 3" or maybe 4" clear above it.

Depending on how deep your rack is, it may end up being open at the back to accommodate the full depth of the amp and the cable connections back there. The backs of 7500 and 990 are both just above flush with the back of my cabinet, with openings cut out for both (making wiring much more convenient).

I plan on putting my 7700 in a rack with only about 1 inch clearance above it. I am a little worried,but my rack is open on all four sides so I'm thinking it shouldn't be an issue. The amp comes tommorrow so I'll let you know how hot it runs.

Perfect...thanks guys!

Hammer, Getting bak to you on the 7700 heat question. Just to put things in perspective, I like my music loud. Ok, really loud, if you listen to my girlfriend.
During normal listening and even when watching movies fairly loud the amp runs only slightly warm. However, when I run music in 5 channel stereo mode and really crank up the volume I can get the amp to run pretty hot. I am going to get a larger rack with more vent space before hooking up the remaining two channels.

"5 Stereo" mode and a fairly high volume do make for a pretty potent test for an amp.

Did some testing last night. With an open rack and about 1 1/2" clearance above the unit I was getting 115 deg. above the amp. I took out the shelf above it and hooked up my 2, 12" subs to the previously unused channels. I now have about a foot of clearance above and open sides. I took another temp reading about 1 inch above the amp and while playing some loud multichannel music I hit a high of 122. deg.
"toasty" you can get this thing hot if you try!