Upgrading to Lion - Questions about disks, RAID and backups
Well you already have a pretty optimal setup. Having the two disks in RAID-0 as your boot drive gives you the greatest possible performance. Just be sure to keep a good backup, since if either disk fails you lose the whole array. Superduper! is great since it makes a bootable backup for you, unlike Time Machine. I highly recommend it. 

Otherwise you're good to go. The only suggestions I have are to buy an SSD for even more performance, and to upgrade your graphics card, you can get a PC 5770 or something for really cheap and it works great.