I love the Pro Logic II Music option on my Tag AV32. It's not science, but magic. I can't understand how PLII knows to have really dynamic surround effects on rock music (eg amazing left-right pans of guitar flicks or cymbal splashes in the surround channels on the early Queen albums I've been listening to recently), but on classical music there is a much more refined 'all-embracing' sound from front and rear speakers. The PLII upgrade for the Tag was definitely money well spent, and I've been rediscovering a lot of my old CDs with renewed enthusiasm.
PLII Movie makes a big difference to my TV viewing as well, not so much for viewing movies on TV (I guess with 5.1 I have become blase about surround sound) but for regular TV programmes. A recent Horizon programme had a narration track underscored with background music. The music was clearly separated from the voice over, balanced nicely between front and rear speakers, while the narration was as clear as a bell anchored in the centre channel. This was a huge improvement over PLI. If anyone is in the market for a new amp I would put PLII near the top of the list of things to go for.
Regards
Rob