At the moment I'm running my i7 behind my TV in an entertainment centre. The cost? Not enough airflow into the computer and a constant battle between fan speeds and acceptable temperatures. The result of which is slower than possible clock speeds and higher than desired temperatures!
The solution? Well I have a nice and cold garage directly below the living room, so I'm "investing" in a 5m HDMI cable & 1 3m USB extension cable to keep our HDTV and my wireless mouse happy. That'll mean I can run my fans as fast as possible, sucking in as much of the cold air as they want, I won't have to worry about the noise of them and I'll still be able to do all the things I do now (game if I desperately want to, watch HD etc).
I mostly use the PC for folding and as a file server these days, usually operate it via VNC & it only has an ancient CDdrive, which I never use as these days I just mount ISOs, I have no need for the PC to be in the same room.
It might even be more secure, because the garage is the last place anyone would look for a computer and at the moment my computer would be the first thing a burglar would see when they lift the TV

PS. time to go get some more memory; can't get enough of it!