Honestly, you wouldn't notice a ton of improvement. If you really want a faster hard drive, the WD6401 AALS is a good choice. It's cheap and has 640GB, and is quite fast. Still, I don't really see why you want a new one if your current one is only 13% full.
The scoop... The faster the HDD the more consistant the traffic pool, the speed of the HDD doesn't affect your gaming unless you don't organize any kind of maintenance to rid off fragments that tend to boggle your drive, as mentioned the RAM is what makes the speed possible. *It seems a major factor in HDD performance is heat beit due to overuseage as it's moving parts tend to decline after hrs of gaming, this is true in RAID configs especially. SSDs (solid state drives) have no moving parts, a plus for the next gen hardware, so you might want to try it out as I've heard it has improvements over the conventional HDD... So your answer is yes, a better hard drive is GREAT for gaming but by better I mean you need to run defraging tools, don't boggle your system with useless aps and large files like video/audio (have a seperate drive for those) and you should be gold.... *If your a hard core gamer, get 74 gig raptor for maybe 2 games that you play often and that you require speed, beef up your ram and rock the latest "BRAIN" Intel's I7 platform