ES.2/7200.10 250 GB versus WD Velociraptor?

So, I've decided that I'm sick of my current WD 250 GB RAID 0 setup, as I'm sure a single drive can perform similarly without the hassle of checking the array during boot as well as living in constant fear of array failure.

I have $300 dollars to spend, so any of these drives are viable options (even the outrageously expensive velociraptor). The main thing is, should I go for the velociraptor given my current 1.5-year-old WD 2 x 250 GB RAID setup? Will I notice a significant increase in performance and system responsiveness? Do access time and I/O speed account for this difference?

If not, then I'm split between the ES.2 and the 7200.10 250 GB drives. The latter is one of the most popular drives and I know it's one of the top-performing drives on the THW charts. The former is server-class and has double the cache at 32MB. Does this boost system responsiveness in any way that's significant? Also, should I consider buying two of either one and making another RAID 0 setup? If I did that, I would probably spend the difference between the velociraptor and the Seagates on a decent hardware RAID card. I could use some guidance on RAID cards too!



All help is greatly appreciated.


System:
OS: Windows Vista 64-bit
CPU: AMD Athlon X2 3600+ 65nm (OC at 2.80 GHz)
Memory: 4x1 GB Crucial Ballistix (OC at 5-5-5-15 1126 MHz)
HardDrive: 2 x 250GB WD Caviar SE16 WD2500KS RAID 0 (16MB cache)
Video Card: MSI HD 4870 (OC at 790 core, 1100 mem)
Sound Card: Creative X-Fi Fatal1ty Champion
Motherboard: ASUS M2R32-MVP (580X xfire board)