I agree that XMS RAM would be an overkill...regular Value Select would work.
A single hard drive with a 16MB cache would be fast (and cheaper) than two hard drives...however, I'm not sure if you'd need two seperate drives for what you want to do.
Defintely get the sound card, especially if you will be doing recording with it. It's quite a jump from onboard to the X-Fi.
"It is the way of man to make monsters and it is the nature of monsters to destroy their makers."