Guitars hey? I've got an Ibanez Iceman ICX-220, and a Fender F-65 Acoustic.
Back to the "better sound" question.. the ASIO sound drivers almost certainly exist for the Audigy... I would start with that. This will allow the output to bypass the Windows Kmixer and prevent it from "messing" with the sound.
Next, ensure that the audio cables from the card to the speakers are clear of any power or data cables.. if they must cross them, try to have them cross at right angles.
Perhaps the most important thing: speaker placement. Keep both right and left channels an equal distance from your ears, and approximately at ear height when in your regular listening position. Try to keep them both the same distance from walls as well, to ensure output is the same from both sides.
If possible, try to get your speakers either mounted to a wall/desk, or onto some heavy stands. Also, good speaker wire can make a huge difference.
Umm.. other than that, get Foobar, and grab a couple of FLAC or APE files to try it out.