Welcome to T.F.!
It's better that you have a friend, to help you build it. Buying the parts are almost always cheaper than buying it prebuilt.
Getting one raptor for the OS and the other for the rest is a nice idea. What you could also do is get two Seagate 7200.10 320GB hard drives, and put them into a RAID 0 configuration.
For that budget I would suggest:
Intel Core 2 Duo E6600
MSI P6N Platinum
2GB of G. Skill DDR2-800 HZs (Since you're doing graphic design, you could go for more ram, as this will benefit the designing program you'll be using)
8800GTS 640mb or an 8800GTX if you can afford
Corsair 620W or HIPER 580W or Antec
For the hard drives, you can go one raptor and one storage drive, or what I said earlier. Two big hard drives in a RAID 0 configuration.
Also an optional aftermarket cooling for the CPU, if you want to overclock. I would suggest the Tuniq.
You should buy from these sites instead, because they have more choices than computer planet:
If you can wait for July 22, there will be a price drop on Intel's processors. You can get a quad core(Q6600), which will be around the same price as an E6600.