Please correct me if I am wrong, however all 15,000 RPM HDDs I am aware of are U320 SCSI.
And SATA 3.0 doesn't exist yet.
Also RAID 0 is fast however the chance something is going to break is increased by a factor of N if you have N drives.
If you have 2 drives it is a factor or 2, 3 drives a factor of 3 and so on.
If money is no problem I would suggest using a Hardware RAID controller like the 3ware 9550SX series or Areca PCI-Express controller.
The 3Ware is PCI-X however so you need a high-end server or workstation class motherboard with PCI-X to use it. Similar hardware RAID controllers from ARECA and others come in PCI-Express versions as well as PCI-X versions and theoretically could be used on a motherboard with 2 fully functional 16x PCI-Express slots.
The 3ware 9550SX can offer 800MB/sec RAID5 reads and 380MB/sec writes.
http://3ware.com/productfaq/3ware.htm
Q2. How is the 3ware 9550SX different from the 3ware 9000 Series controllers?
A2. The 3ware 9550SX controller delivers over 800 MB/sec RAID 5 reads and exceeds 380 MB/sec RAID 5 writes, making it 200% faster than the industry-leading 3ware 9000 Series controllers. The 9550SX is a SATA 3Gbps (SATA II) controller, while the 9000 Series is SATA 1.5Gbps (SATA I).
I can show you some 3Ware 9500 benchmarks if you are interested.