I'll add my two cents. I have owned or put together computers with the following:
IBM 75GXP
IBM 60GXP
Seagate Barracuda IV
WD 1000BB
Maxtor D740X
From quietest to noisiest: Cuda4 which is inaudible, followed by the D740X which is very quiet (can't hear over case fans),
followed so closely by 60GXP that it's hard to tell the difference between it and a D740X, then the WD 1000BB and the 75GXP.
The last two you can hear seeking, but you couldn't say that they are loud.
In terms of seek time, the stats are out there somewhere, but my memory says, in order from fastest to slowest:
IBM 60GXP, IBM 75GXP, Maxtor D740X, WD1000BB, and the Cuda4. The difference in performance from fastest to slowest (in terms of average
seek time only as reported by HDTach and quoted from memory) was around 30% with the IBM's at ~10.5ms range, the Maxtor ~11ms
range and the WD and Cuda4 in the ~13ms range.
I'd probably vote for the 60GXP based on the seeks, although either way you come out a winner.