The Nightstar Zoo

We've all heard that listening to classical music can help you concentrate, improves test scores, brings brain cells back from the dead, etc. Well, if at all possible I'd rather study to classical-flavored rock -- progressive. Can anyone recommend some mellow prog-rock tunes that would make good background music for my studying?

So far I've got:
- King Crimson: Epitaph and Court of the Crimson King
- Pink Floyd: Us and Them and Shine on You Crazy Diamond
- Moody Blues: Knights in White Satin
- Yes: And You and I

Keep in mind that I'm largely ignorant of progressive except for some Yes and Pink Floyd albums, so if I haven't listed any others it's because I'm not aware that they exist.

Magma
Henry Cow
Univers Zero
Art Zoyd
Present
Kultivator

This is the deep end of the pool though. Proceed with caution.