If you want to be future-proof for the next year or so, and want to take advantage of EAX 4 and 5 (still not many games actually support it) I wholehearteldy suggest the X-fi extreme music. I've posted a bunch of stuff on it before, and I feel it's a superior card to the Audigy 2 series as a whole. I absolutely adore it, and I feel it was worth every penny. It really wont make a difference though as I've said before in sound quality if you use cheap headphones/desktop speakers. If you have a decent pair of desktop monitor speakers, or a good hi-fidelity set of headphones, then you will be able to notice a difference, if you really pay attention. (or are like me and have abnormally sensitive hearing)
That, and I'd also reccomend the new X-Fi, so you'll get new drivers here and there. Creative stopped supplying decent drivers for the Audigy 1 very shortly after the Audigy 2 was released, and from what I heard from my gaming buddies locally, the drivers werent so hot either