Definitely add a few items---
Liscensed OS--- I like winXP (gonna try Linux when I have the pc all to myself)
Logitech Z-560's--- perhaps there's better/more expensive out there, but these are already overkill. I guess you could get a couple of splitters from radio shack, and plug 2 sets of them in to your sound card for an 800W system. (again, overkill)
Good Keyboard/Mouse-- I like the Logitech cordless freedom optical for $79 at costco
good chair--- your buddy will have to select this himself. A chair is very personal. I prefer a nice, high-back reclining model with good lumbar support and fabric that breathes.
Other input devices-- good webcam, joystick, gamepad, steering wheel with pedals.
Games. Lots of them. Absolutely do not miss Operation Flashpoint
ONE MORE THING
Get 1 more of everything and some networking goodies. Lan gaming is good!