your results with CoreAVC/cuda are better because of... cuda
Well, the point is... they are actually not
Standalone Mencoder_mt works better in my case (C2D 6300, GT 9600 GT) than Mencoder/CoreAVC. That is the whole reason why i started researching the problem of mencoder doing badly with MP4+external subtitles, cause my 1080p videos do not stutter with mencoder_mt and DO statter with CoreAVC.
But most of them are mp4's
Anyway, thanks for the info, i'll try to find some optimal combination... or upgrade my PC