Stay away from generic or no-name PSUs (Power Supply Units). Too many times have power supplies been advertised as 400W (should power just about anything), and they can't get the computer to start with the video card plugged in only. Let me give you a name of a PSU that gave me trouble--EVER. Don't use their PSUs, they suck. Spend a little bit more that goes a long way. Good brands are Enermax (inexpensive, and good quality), and Antec (which is a tad expensive but good quality). Don't use too much thermal grease/compound, you want it to conduct to the metal heatsink, not become its own.