I have a 1st generation mac pro, 3gHz, 4GB RAM. I'm looking to get another hard drive in the machine, 500GB. I was looking at macsales.com, and I have a preference toward Seagate with my background. Unfortunately, I don't know much about the subtle difference in speed or performance with newer drives (ES-2 Enterprise-Class, for example). I was looking at a couple on there: 500GB Seagate Barracuda 7200.11 SATA II 7200RPM 32MB Cache - 5yr Seagate Warranty 500GB Seagate Barracuda ES-2 Enterprise-Class SATA II 7200RPM Hard Drive with 32MB Cache Do you have any recommendations for me? Obviously, speed and it being quiet are my top preferences. What's the best bang for my buck? Thanks for your input very much.