The config you are talking about would only give you about 140 gig of space for over $6000. If you want speed and redundancy you should fill up a cabinet with 18gig drives.
I personally switched from a Dell array to the Apple xRaid. It's cheaper, has more storage, fast enough and gets the controller into the drive array where it belongs.
Plus when you discover your 32bit machine is to slow the xRaid will work on your new database server
