I got a WD 8MB Cache. I like it because it is very quiet. I can't hear it at all. If I put my ear up to it there is a nice deep pitched hum, unlike the typical high pitched whine of my old IBM 7200.
For some reason UT2003 runs a lot smoother on this new drive. No more stuttering and high detail. There may have been a problem with my old drive, even though the IBM diagnostic tool doesn't show anything wrong with it.