I use a AMD Athlon II X2 235e / 2.7 GHz Energy Efficient processor. This is not a very fast processor, and even slow Atom processors can handle full HD. The real important thing is the videocard, the videocard has to help decode the HD-files. I use 2 Gb of ram. If u wanna know more check "My System". A quadcore is overkill for a simple HTPC.
I use an onboard videocard, the ATI 4200 wich is good enough to help decoding. So every ATI Radeon wich is newer/faster (4000/5000 series) than this one will work (with propper codec installation).
PassMark CPU Benchmarks - Low End CPU's
There is no way you play 1080p on that setup. I have an E6600 and an ATI 3650 and I can barely play 1080p using ffdshow tryouts and haali and coreavc for x264
United States of America