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!