I'd
highly recommend against a Western Digital special edition drive (the ones with the 8 MB cache.) I have one in my iMac DV, and it's super fast and fairly quiet. It's actually very quiet compared to the original Maxtor that shipped with the machine (and the Maxtor was a 5400 r.p.m. drive, while the WD is a 7200 r.p.m.) Anyway, the problem with the drive is that your iMac likely won't sleep with the drive installed. It will continuously spin down and then spin up again the entire time. Not a good sound, and I'm sure it's not good for the drive. This is an issue with OS 9, Jaguar and Panther. WD says this is an issue with Apple, and Apple doesn't seem to care. There are quite a few threads about this on Apple's own boards, and reader reports over at XLR8YourMac as well.
An interesting thing though...if I've booted with my FireWire drive, sleeping works just fine. I can't figure that out.
Anyway, that's my sad story of a very tired iMac...
