I have read that this 650e fits in above the HD7750 but below the HD7770 ... however one test review claimed it could be overclocked to very near the 7770 performance. I may try sometime to do that. But as you pointed out the cramped quarters had me worried about a hotter board like the 7770 .... plus i think a PSU upgrade to 400+ watts might be best for the 7770.
I read somewhere that those 4800 ran pretty hot ... i expect thats why mine failed in the confined quarters ... i never thought to check the temps.
KC