I am using a Maxtor Diamond Max 2500 Type 91000D8. 7200 rpm and excellent seek-time. Clicks are very rare. Maxtor have improved their disks further, so that if you buy a new Diamond Max Plus you should have a very good disk for GS.
The new Quantum KA-drives have smaller caches (though they claim to have 512 kB) though they rank among the top in test-magazines. IBM DJNA-drives with 7200 rpm should run fine. Western-Digital Expert (7200 rpm) drives have big caches and good specifications but are horribly noisy. The rest on the market is falling behind the current state-of-the-art IDE-Drives.