Failing audio

[Jostein G. Holte]

Dear cubists!

I have a Cube with stock 450MHz processor, GF2 (from tower), 512MB RAM, 
Airport (grey base), original ball-speakers and iSub.

 From time to time the audio becomes "muffled", most often this occurs 
when the CPU load is peaking, but it also happens at regular cruising 
speed. The "muffle" stays on till I sleep/wake the Cube or 
disconnect/connect the USB audio cable. I can almost live with the 
"muffle" but recently audio has started to stutter for short periods 
and sometimes completely fail. Resetting USB will normally fix this 
too, but it happens way to frequently for that to be an acceptable 
solution.
Has anyone experienced anything similar and managed to get rid of the 
problem?
Would an iMic™solve my problem?