I'm not sure if anyone is still reading this, but here goes:
First, let me say that Nero Recode is, by far the best, DVD to PSP conversion software. I have tried Copy DVD, PSP Video 9, and several others. Second, the best tip I can give is to not use DVD decrypter at all. DVD movies are roughly 9GB or so, and copying them to the hard drive at 5.8GB will degrade the quality. My Advice is to grab a copy of ANYDVD. It allows you decrypt, on the fly, commercial DVDs (along with HD-DVD and Blue Ray) that you already own, of course. With ANYDVD running in the background, fire-up Nero Recode. Pick your audio stream. Recode does tend to have exceptionally low volume, but there is a volume boost under settings. Set the Digital profile to Memory Stick Video AVC. In order to play H.264 AVC video you'll need to have 2.5 Firmware or Higher, but this can be emulated with the newest version of Devhook. You can now set the out-put file's size limitations. It doesn't really need to be bigger than 256MB. I've found that, that size using the H.264 codec makes perfect video. It has a small screen initially, but fits nicely when zoomed in upon, and H.264 doesn't lose quality even when zoomed to full screen. Hope that helps!