Audigy 2 cards with original drivers need some fine tunning with Graphic Equalizer. Otherwise they sound dull and unimpressive. Boosting lower and higher frequencies gives incredible results.
My EQ preset:
http://img524.imageshack.us/img524/4969/cteq0ac.png
You may want to fine-tune 1k slider. I prefer it up there but you may not.
Move 125 slider higher if your subwoofer allows that. Mine doesnt hehe.
Move 8k slider higher if your satelittes can output higher freq. without distrotion (mine again can't).
Also sound is pretty subjective thing, but it sounds the best on my Cambridge SoundWorks 4.1 speakers (with CMSS1) with some resampling on WinAMP's end (Shibatch decoder and SSRC). Excellent sound.
Good thing is also that Creative EQ boosts the ingame sound. I'm playing old Rune game at the moment and sound is really breathtaking. Same for Quake 3 Arena and CounterStrike:Source (blasts are stronger and ejected shells sound more metal like when they hit the concrete ground). It's worth a try. I simply can't live without this thing
But sure, X-Fi is one hell of a beast. Though still a bit too expensive. Price should fall for 1/3 and then it will be worth considering it (Audigy 2 -> X-Fi transition).
If you run some onboard crap you probably can't miss much with X-Fi either way regardless of price. Soundcards don't change often anyway.