Upgrading Raptor?

[skyline889]

I have a 150GB Raptor right now and was just curious what I would need to buy to see a noticeable upgrade in performance. I know the 640GB WD drives will offer better transfer rates but does that make up for slower access times? I might upgrade if I can do it for $100 or less but if I'd need something like a V-Raptor, I'll probably put the money to other use.