I used 2 of that Thermaltake fan on my 722 when I had one last year to push air in and pull it out. The shelf it was on was enclosed on all sides but the front. Even with an open front my 722 would get real hot and reboot on it's own. It helped keep the temp reasonable. I bought this mini surge strip with usb ports on it and used that to power the fans.
Amazon.com: Belkin Mini Surge Protector Dual USB Charger: Electronics
One of my hoppers was in an enclosed cabinet and I was concerned about the heat since I had that problem before. The installer said it shouldn't be a problem. I went ahead and let him put it there but the more I thought about it the more I wished I hadn't. I only wanted the hopper there so I could have PIP. I decided to change things up so I switched that hopper with a joey that was upstairs in a study. The TV is on the wall above a fireplace so I used command strips to mount the joey to the back of the TV. I really like how it works and looks now. I used the HDMI cable I had in teh wall to put my blueray player in the cabinet since it isn't on all the time.
