Homebuilt upgrade with low fixed money

My limit is 500 dollars but if over a little bit I might consider too.
I will be using the computer for gaming, video editing, overclocking and other stuff.

I'm planning to upgrade my processor, motherboard, video card and power supply.
Processor: Q6600 - I need to find somewhere cheap.
Motherboard - Don't care which one as long it has future upgrade but it has to compatible with DDR2 667 PC2 5300
because I will be using my old RAM for now. I might consider upgrading RAM later now.

Case - Thermaltake Shark(Have this already)

Video Card - ATI X800 I believe lol. I'm pretty sure I need to upgrade this to play todays games.

Power Supply - Suggestion?

Other parts I forget to mention will be upgraded later on when I have the money. Money getting tight these days.

Thanks in advance

Invent a time machine, go back in time to Black Friday, and buy a Q6600 from Fry's. They were like $199 or $179 bundled with some crappy motherboard, but you could just toss it because you still made out like a bandit on the deal.

If the time machine idea fails, you can find the Q6600 on newegg for ~$279 last I checked. You may be able to find one on ebay, but I just don't trust 2nd hand electronics because you can never tell what was done to them before. (Like some OC-noob hurting a chip by OC'ing incorrectly)