RAID 0 would give you the best performance. But remember there is no fault tollerance for RAID 0 so if you loose your data its gone forever....My best advice is to go ahead with the RAID 0 array and have a stand alone drive ( of a size that fits your needs) to store all your important stuff on, or a external usb drive works good to periodically backing up your "have to have and important stuff"
It probably be better just to do a fresh install on the Raptors. You will want to use their speed for boot times, general file paging, loading programs ect ect....
You have them monsters so USE THEM FOR EVERYTHING !!!!! ROAR LoL
You must have a ton of programs that autorun at load. My System loads in less than 45 seconds from a dead boot.And I have 4 programs that run at startup.
Anyways you should see a significant performance increase in boot times.
from 7200 - 10000 rpm I found a noticable difference on boots. mines around 30sec to desktop. about 25 on a clean install. vs 60 and 45.
from a min 20 you'll probably see it drop to 40-50sec. the 150's + RAID is a dream for most. if you can afford it get another 150 and RAID 5 the 3 drives. the only thing faster would be a set of 750's in RAID, but a $1000ish is a little much.