I'm puzzled then. I'm pretty sure JimH recommended Red October HQ to me for my DVD playback requirements. When I switch between standard and HQ I seem to see a difference. HQ seems sharper, and to have more punch. I had a thread elsewhere here asking about using videoclock and reclock to get stutter free playback with Red October HQ on DVDs. On Red October HQ with Videoclock I get a 2-3 second long stutter every now and then... the video sort of strobes... On standard I don't get it, and on HQ with Reclock I don't get it. I now find that if I tick hardware accelerate and use Videoclock I don't get it on HQ either... and the picture looks good. And with Videoclock I get better sound than with Reclock. (I let JRiver decode, then later repackage as AC3 for my spdif connection to my Yamaha receiver.
My machine should be ample fast for any of this... its a Core2Duo, 2.66GHz, 4 GB RAM, Asus GT440 video card, Windows 7 home.
What I'll have to do is look at the filter graphs to see what they say, but something isn't stacking up...