Let me start by stating that both SX and 5.0 are originals.
The problem was also in 5.0, but less of a problem. But I trully believe it has something to do with Pulsar, or my computer managment. Disabling onboard sound and USB didn't really help.
Sound stutters...
What I would do is check msconfig and uncheck everything possible under startup tab. Then turn off your computer and take all the PCI cards out except the Pulsar. See if that works and if not try putting it in a different slot and booting up again. It is possible you have some cards shairing some resources. I have a similar motherboard with a pentium III and it works perfectly at the fastest setting although I have it set to the second one for a little more elbow room.