I downloaded just the Chorus Mysticus track from iTunes, just to get a feel for the ending of Part II. It is indeed a grand drawn-out ending with VERY audible tam-tams and a powerful bass drum roll. However, the orchestra doesn't seem to have enough "bloom" -- although perhaps the MP3 (which is a fairly high-rate vbr) limits this to an extent. The organ could stand to be a bit better, but it seems pretty decent.
I'll certainly order this from Amazon when it's released, but will not repeat my previous practice of purchasing through the SFSO site -- since they are selling it for $40+ (including shipping).