What I found was that it did have less hiss and noise but I had to connect it to a rather big speaker set to notice it. On the headphones I could barely tell.
NOW THERE IS ONE AREA THAT WAS REALLY BETTER. This was the audio capture. That was definitely many steps up.
Hope this helps,
I have a new HP Pavilion a1510n with XP MCE 2005. It has the built onto mother board sound (AC 97) with Realtek drivers. It sounds ok, but I have wondered if I would notice any real inprovement with installing a seperate sound card, or would that just be more money for negligible improvement?