I have not heard the Anniversary Apollo - but I have compared the Saturn and the standard Apollo. The Saturn is more polished than the Apollo - you might almost call it polite in comparison, but it didn't grab me. I almost preferred the sound of the Apollo to it's more expensive sibling, at least when mated with other Rega gear and some nice Naim monitors. Not sure the Saturn is worth the extra pennies from the heavens. If I was in the market for a player in the 2K-3K price category, I would probably look elsewhere, for example at the Naim CD5x, which is often displayed right beside the Saturn in many hifi shops, even at the 5x100 higher asking price.
But to be fair to the Saturn, read this:
http://www.positive-feedback.com/Issue35/rega_saturn.htm
and this:
http://www.stereotimes.com/CD091806PS.shtml