Sorry, I did mis-speak - fingers working faster then the brain...again...RAID 0 is what I was meaning, and writting RAID 1.
Huskerfan,
If you feel you must have faster then what you currently own, go with the new WD Raptor 16 mb gache drive, forget the RAID, and get a large HDD for data storage and backup. Although the 750GB is a good reccomendation, it may be overkill for the cost per GB, as there are some good 300-500gb HDD for a better cost/gb ratio. You could buy two smaller drives that will yield higher total storage capacity for almost half the price of the single 750gb drive. In all honesty, your 74gb drive is going to be plenty for gaming applications. The only potential draw back is that you will have to put your OS and your games on the same physical drive to get the performance gains. IF it becomes *that* critical, a second 74gb WD drive would probably be the best cost/performance gain (for storage options). If money isn't an issue, buy the 150gb raptor, use that for all your high end games, install the OS on the 74gb (on maybe a 25gb partition), and buy a 400+gb HDD for storage.