worth getting a sound card?

[teratravp]

I'm using onboard audio right now. AC97. Honestly there aren't many problems and pretty much everything I play sounds and plays fine. But I read a benchmark of an audigy 2 zs and it was getting signifigantly higher framerates - as much as 20 frames over other sound solutions in games.

2 cards I've heard good things about are the fortissimo III and audigy 2 zs. I'd like to stay in the low $50 price range so unless audigy can give unrivaled performance boost in games, forget it. there's also turtle beach santa cruz around that range that's supposed to be good. I have little interest in sound features and musical extras, lot of interest in performance enhancement for games. that in mind any recommendations?

and one further thing, I might be overhauling my system soon and problem get an nforce mobo with it's lauded onboard sound. don't know how that stacks up but if that's comparable to sound card performance let me know and I'll wait for that.