Moth3r said:

More information on the upmixing process here:

http://originaltrilogy.com/forum/topic.cfm/Doctor-Ms-Stereo-to-51-Dolby-Prologic-II-Upmix-Guide/topic/11546/

I surmise the default 20ms delay are corresponding to the stereo widening process... I would go easy on that if it is for classical music experience or so... As I said, it sucks the dynamic as far as I observed. But well, it is your laboratory now! ;)

Edit: the stereo widening filter I have at hand is the one from Nero Burning Rome, wich is convenient to check in real time the fx. You'll spot right away how it alters the EQs and then be able to compensate if needed. I'm not sure it is the same processing than the delay I just mentioned though. As it seems your search is for "audiophile" purposes you would won by testing separately such alternatives.

Have a nice time.