I have to admit this is something I'm looking for. I really like the low profile cases because they tuck underneath a TV and looks like it belongs there. but they all only use low profile cards, which basically limits me to a 7750 (or a 7850 if i can actually find it).
There have been riser cards since sliced bread, so it should be fully possible to make these cases. do you know of any?
As far as cases go, a low profile case is only ment to fit low profile cards so unfortunately your best bet is to go with a 7750. For light gaming in 720p it would be a great option but just dont expect it to perform crazily awesome. Another option is purchasing a mitx or matx case as they tend to be smaller cases that fit full sized graphics cards but may not fit under your TV.