if i was you i would stick with the 7200 rpm. i have a 7200 rpm and i love it adn 27 gigs is pretty hard to fill up. One more thing as time goes by Programs and games are required to have more and more power to pump out and getting a fast hard drive , i think, will help you out more then more memeroy.
So go what ever your price range takes you

and Just to tell you what kind i got and tell you how it runs:
Western Digital 20.4
7200 RPM's
And i never had a problem yet with it (IT is fast)
so go get you what you need fast or more space!!!
sorry for all the grammer mistakes