I want a fast internal HDD?

I have a 230 GB HDD that is pretty slow. I have a Dell Inspiron 580 with a core i7 2.8 GHz Processor and the default motherboard for the Inpiron 580. I have 4 GB of 667 MHZ ram and a 512 MB nVidia video card (forgot which one it was). My current HDD is the WD Caviar Blue 320 GB SATA Hard Drive (WD3200AAKS). That being said, what is the appropriate HDD to get that is fast. I DO NOT want an SSD and everything stored on my computer amounts to about 50GB. As you can see, I dont care much about size as long as its above 80GB. I just want performance. I have a budget of about $500, I need an HDD that has a fast avg read/write speed for HDD's. I was looking for HDD's with 15,000 RPM but I don't know which one to get. I need it to be optimized for gaming (specifically GTA and M Effect), the faster the better. Company is no difference to me, just so it fits in my Inspiron 580, and thanks to anyone who suggests some.