@spaceman if you need/want to run raid 5 try running raid 50 instead if posible ( raid 50 requires min of 6 drives ) . spanning 2 raid 5 arays in raid 0 .
High data transfer rates achieved do to its RAID 5 array segments
High I/O rates for small requests achieved do to its RAID 0 striping
should help boost performance ! other wise go with a raid 0 setup. i have 2 of the 7200.10 seagates 320gig 16mb drives in raid 0 and they are quite fast.