The biggest things a third-party audio interface will get you are better quality audio I/O and lower latency than the onboard chipset, typically in the 6-10 msec range. I do suggest that you consider something other than the Audigy. Its sound quality is fine, but it is oriented towards games and movies. If you plan to make music with it, a dedicated audio interface will offer a pro-level signal path and full-size jacks as well as other features determined by specs and accompanying software. If you have old-style MIDI gear with five-pin DIN connectors, look for MIDI I/O as well. You will get plenty of opinions here as to what is best, but you can do fine in the same price range.

HTH,

Richard

"My primary musical instrument is the personal computer."