Some issues you may want to consider b4 commiting to a PC setup.
1) If you're using Adobe CS, get a dual core processor, or even better, get a multi CPU machine if you can afford it. CS runs multi threaded more efficiently on these machines.
2) If you're shooting RAW buy LOTS of RAM, recommended 2GB.
3) If you don't play games, get a good 2D graphics accelerator like the ATI firegl v3100 and calibrate it.
4) Don't bother with software RAID, get hardware RAID and create a type 1 array, type 5 if you have the money.
5) DO NOT put your OS/programs and your pics on the same hard disk array.
6) Have one more hard disk as the virtual memory disk if you can afford it.
7) Get as BIG a casing as you can stand, big casings with lots of fans are good for the health of your PC.
8) DON'T stinge on the power supply, get an accredited power supply unit which can deliver at least 480W constant. (Trust me, this is the 1st thing to die)
9) Blow you entire paycheck on a good monitor, it pays if your pics earn you a living.