Hardware Requirements - XBMC Eden 11 with Pixel Shaders (Spline/Lanczos)

Hi,

I'm wanting to run an XBMC PC that upscale standard SD content to 720p.

Before XBMC 11, we had to use MADVR to get the best upscaling. But apparently XBMC 11 offers just as good quality without the need for an external player/MADVR.

So:
1) What are the minimum requirements for an "XBMC only" Pc that will match the quality of MADVR (assuming pixel shaders and something like Spline/Lanczos upscaling is used)? What graphics card/CPU should I look for as minimum?
2) Could I get away with using an Apple TV2 to do the job? Would the results compare to using a full PC for 720P output?

Thanks in advance!