" 3 HD setup, would one74gb Western Digital Raptor WD740GD and 2 80gb Western Digitals for Swap and Data be a good choice? Does this need RAID...... or would simple partitioning suffice?"
No, you do not
need RAID... I'd prefer using separated disks than a RAID array (because the controller also could fail)
There is not so much need for partitions, NTFS is not so prone to fragmentation, and the Scratch disks less sensitive to that issue (as long as it is on a moderate level)
Put the scratch disk and the pagefile on separate physical disks.
You'll love your Raptor. It is not so noisy nor so hot- mine is placed in an Silentmaxx enclosure-. (large HD's with a lot of platters can be noisier and hotter, as you could see at
www.storagereview.com )
Pay also attention to the noise of your machine: a 120mm fan does need to spin slower than a 92mm one, see
www.silentpcreview.com