Running a SoundBlaster Live! 5.1 and it's been solid for years. The new Audigy is $80 and claims better audio quality, hardware EAX 3.0, and a FireWire port.

Is the audio quality difference actually noticeable? Or is this just Creative selling me a new version of the same thing?

The audio quality improvement is marginal for most people. If you're an audiophile with nice speakers/headphones, you might notice. Otherwise save your money.

EAX Advanced HD in supported games is genuinely impressive though. The reverb and environmental audio effects in games like Unreal Tournament are much better on Audigy.