Any 3.5" SATA drive will work. I suggest either Western Digital or Seagate. I got one of these for my early 2008 iMac about 6 months ago and so far I'm delighted with it. I didn't benchmark it so I don't have any hard numbers, but I've found the performance (copying between partitions, or hashing/encoding files) to be easily double that of the Seagate 7200.10 320 GB drive that was originally installed.
(I wasn't sure, but bare drive just means that it ships in an antistatic bag rather than in a retail package, which suits me just fine. The shipping box is filled with plenty of packing materials anyway.)
My Mac Pro came with a Western Digital HD I have installed two further drives, both Hitatchi, I would not have a Western Digi drive by choice, I have had too many problems with them failing in the past, although the one in my machine has not let me down yet.