I also have the NSK2400, and am using a very old i865 Intel motherboard and northwood P4 processor that I got for free.
I am exclusively using this computer to play ripped DVDs upscaled with ffdshow and output at 48Hz (via powerstrip) to my projector. The problem is that ffdshow's LimitedSharpenFaster is so demanding that I can't use it without stutter.
Have you experimented with ffdshow, LimitedSharpenFaster, or Avisynth on the AN-M2HD?
If you're unfamiliar with this, see the massive thread at avsforum here: FFDShow Walkthrough
. Basically, you can run Avisynth scripts inside ffdshow. LimitedSharpenFaster is one such scrip, that employs very decent sharpening algorithms. But using this scrip after resizing is just too much for my P4.
I'm curious to know if your X2 5000+ and the AN-M2HD can handle lancos resize to 1280x720 (or higher) with LimitedSharpenFaster (the "Intermediate" config in the link above).