I guess computer gaming is like any other hobby. I just love to buy parts, build my own system and then tweak the cpu core, overclock cpu and gpu,... fun but expensive if you screw it up.
Btw, computer gaming (and some extend graphical applications, servers) is what keeps the computer industry going and bringing new records to the industry. You sure as hell don't need a dual core, 3gb or ram, 2 sata 300gb HD, watercooling system for your cpu; to download music, watch porn, or use MS Office.
2007 is going to be an expensive year if you are into building your own system.
Now a good video card can cost you almost 1/2 of your pc budget if you don't want to buy a low end card.
Just as example, the shitty PS3 will be obsolete vs pc gaming in less than 6 months, but most people can't just shell out 2K$ for a top of the line gaming system.