get seagate barracuda its around 9k at ink tec opposite of barclays at unity plaza
but the thng i there is a small fault in their bios u hv to update it.
Since you mention the size as 500GB i'd say best option is 500GB Seagate SATA2 driver. Which you can buy for like 9k @ EGS. its got giant 32MB cache where almost all the other hdds have 8MB
IN general Maxtor & Seagate are good reliable hdds.