Help with choosing CPU and mobo for media pc

Specs so far:


Modular PSU: Corsair 450 HX
HDD: iTB Eco Green
Operating System: Windows 7 32-bit, using MCE as the front end
Case: Antec Fusion Remote Max
Optical Drive: LG Blu-Ray
RAM: 2x2GB of RAM (brand and speed undecided)
TV Tuner card: Black Gold BGT3595 (apparently coming out next month)

Build needs to be as efficient and quiet as possible but powerful enough for bluray/1080p and streaming live tv to other computers/media extenders while recording 2 or even 3 channels at the same time (though this will not happen very often).

I have discounted ATI chipsets and have plumped for the nvidia 9300 or 9400 onboard graphics boards (can be full ATX as the case can take it, but not necessarily).

Would be grateful for your advice on the best board and a decent duo core cpu to go with it.

Thanks