Configuring a new Mac for FCP

Hi All, I need some advice with the configuration of a power mac for Final Cut Pro Studio 2 editing. I am upgrading to a Sony EX3. My concern is storage and process speed of the drives with HD footage. Should I make an internal RAID from the fast 300 GB SAS drives or get the 1TB ATA drives. This is the configuration I am thing of getting:

Two 2.8GHz Quad-Core Intel Xeon
2GB (2x1GB) add 2GB later from Mac mall
4x300GB 15,000-rpm SAS plus Mac Pro RAID Card
or
4x1TB 7200-rpm Serial ATA 3Gb/s
or
1x750GB 7200-rpm Serial ATA 3Gb/s
1x1TB 7200-rpm Serial ATA 3Gb/s
NVIDIA GeForce 8800 GT 512MB

Thanks for your attention