The "double-disc sets" released with Special Edition in 1997 make total of 6 CDs for the old Trilogy. Most of the music was re-recorded for Special Edition - the difference is most noticeable with the first movie, since it's the oldest.
Judging from the equipment you have, you're a hardcore audio freak, so I suggest you to obtain these three 2 CD sets, to be able to compare the two releases.
I'm also a "Williams-maniac" and I have them both
But you may want to wait until the Trilogy gets released on DVD, since Lucas is gonna to release the soundtrack, too, to empty the fans' pockets from the last saved cent (or grosz).