Well, after reading lot about ffdshow, i came to conclusion that ffdshow is very good at decoding & scaling. However, it also has some disadvantages - it is very CPU hungry & presently doesn't support DXVA..
Actually - it will run perfectly well on any C2D with all the post processing settings enabled -
POSTPROCESSING
Presets (highest quality - slider to the right)
Processing Method
mplayer
accurate deblocking
level fix (luminance on)
The only time when I see high CPU usage is when the SPP deblocking options are enabled, and those don't make a immense difference over the mplayer PP method.