Slack 9 using aRts. Not sure about sound card, it is onboard, but the mobo is Intel 815 chipset? I think. Uses video drivers for I810, and it is onboard as well. I have been trashign around with the mixer in KDE, and moving every knob and switch, and it is a bit louder, but still considerable quieter than when using Windows.
I don't think it is hardware because it works, just quietly. Sucks when I forget to turn down the speakers and the wife boot to M$ and it about blasts out the eardrums.