Hi
This is just my opinion but I would go with two hard drives and no raid.
I would rather have my hard drives independent of one another.
I back up all my data on the second hard drive using Norton Ghost.
This drive also has a complete backup of drive C: so that it can be restored using a boot DVD, in case the drive fails,
Windows crashes or I get some really bad virus or something.
As an added precaution I back up both of the drives in the computer to an external drive that can restore either drive as well just to be sure.
Don't scrimp on hard drive space, two 500 gig drives are very cheap now and you can get and external drive for about a hundred bucks.
If you have years of photos and job files as I do you can't be too safe.
If you wan't a really powerful computer at a fair price check out the basic Falcon Northwest Talon, or look at the specs.
Two of my friends have them and I have a more powerful version of one myself. Photoshop runs so fast it is hard to believe compared to my previous computer.
Mike