Ok, if the system idle process is reading 92~97, you shouldn't be having a problem with being swamped with processes.
When you said "played direct from the drive", do you mean your CD Drive, HDD,or everything you play? If it's only on the CD drive, perhaps it's not the sound card but dirty lenses...? If it's the HDD.... I've really no idea. If it's both, I'm inclined to believe that it's either the sound card or the speakers... Sorry, I'm not too good in this area, but I hope I helped!