+1 on first reply. The X4500 won't get you as flawless a playback experience as you'll want. In terms of heat, it's hot but if you have a case with good airflow it's not a problem, at all. The E5200 is perfect for this sort of stuff and I would hesitate going lower than that. I'd worry about a PSU that comes with a case, they aren't high quality units, but as a stop gap it's certainly fine. That's a great build you have there, what ever mobo you choose you'll get plenty of support in their respective threads here. Good luck.
jason
jason