I have my budget around $3k for the box only. Monitor's, keyboard, etc I buy once in a blue moon. I spend top dollar on that stuff. They should last me 5 to 10 years if I don't mess it up.

My rig's life span I try to make for 5 years. So I spend alot but only once in every 5 years. I may do some upgrades depending in between.. but normally not needed. Unless companies like creative screw there clients and force you to buy newer products because they've abandoned there older stuff. like the Xfi elite pro. When I bought that it was $500+.. For XP it was great. For vista it is a nightmare. For Win7 it works with PAX drivers. but creative sucks now.

Anyhow just becareful on what your spend. Do some research on there forums and see if there products are good or bad. Make sure you parts are compatible. Otherwise it doesn't matter what you spend, since it can be all a waist.