OddTSi - Yesterday, I replaced my SB 5.1 with an Audigy2 ZS, and I think it was well worth the price. Gaming sound is noticeably better, and music is a LOT better. I have a Y-connector splitting the front channel off to an old class-A Yamaha preamp, which I use for listening to music with headphones. It's a much bigger improvement than I expected. I think it's worth it just for music alone.
While I'm on the subject, I had an odd problem after installing it. When playing Soldier of Fortune 2 online, I would get halts for several seconds at a time, and this happened about once every 30 to 60 seconds. I tried a couple of different servers, and got the same result. I checked my IRQ's, and the sound card was sharing IRQ 10 with the network card. I thought WinXP didn't really have IRQ sharing problems, but I decided to move the sound card to another slot. It changed the sound card to IRQ 12, and the problem was gone.
Edit: Teh spelling.