Here's the components:
 
mobo:  ASUS P5K DELUXE/WIFI-AP LGA 775 Intel P35 ATX Intel Motherboard  $220
 
CPU: Q6600 $266  
 
Ram: rucial Ballistix 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory (two) $160x2
 
Case:  Antec Performance One P180B Black $130
 
PSU: SeaSonic S12 Energy Plus SS-650HT ATX12V / EPS12V 650W Power Supply $160
 
Video Card: x1900xtx $0 (I own this. I am waiting for better DX10 cards to come out, plus this allows me to get 4 gigs or ram, a better mobo as well as a liquid cooling system.)
 
HDD:  Western Digital Raptor WD1500ADFD 150GB 10,000 RPM 16MB Cache Serial ATA150 Hard Drive $195
 
I own a monitor, keyboard, speakers, printer, etc.
 
 
Is my power supply enough for a heavy oc on a Q6600 w/ the extra components?
 
Total $1231

Hmm from what I have been told you will need a bigger PSU, especially if you want to OC.
 
Perhaps a 750-800w or even just go for 1000w to be ultra safe?

Absolutely, the Seasonic S12 is a behemoth, one of my personal favorites, you can pretty much power a rocket to the moon if you'd like with it. If for some reason you want another option, there's always my other 2 favorites on that power range and it's the PC Power & Cooling Silencer 610 and the Corsair 620HX. Any of those three will power almost anything that you'll attempt.

And to the guy above, he may get a high wattage, lower quality unit for the same price, but these things are made with top quality components only surpassed by bigger PSUs with the same kind of quality such as the PC Power & Cooling Silencer 750W or Enermax Galaxy 1000W. (And those two are made exclusively for insane power needs only, something you don't need to even worry about)  

Looks good.  
What will you use the quad-core for?
The Yorkfield is around the corner and will be a lot faster in media applications. But then your mobo can add a Yorkfield and the Yorkfield will cost a lot more than $266.
The x1900xtx is a smart move. You can find a x1950XT even cheaper.
I bought a similar system a few months ago. Funny how that $1000 adds up to $2000.

I looked up my rated wattage on the extreme psu calculator and with everything I will be running, including a pump (swiftec mcp 655) for a liquid cooling system,  it comes out to 563 watts. The 650 watt technically should handle it. I am just not sure on how well it will run with the overclock. I want a seasonic for the low noise and high efficiency. The extra 50 watts for the 700 watt version runs an extra 50 bucks.  
 
As long as it will work and I can simply run a high oc (i added in a 3800 mhz oc w/ 1.5v for 239 added watts, which is in the ball park of the G0s) I am happy.
 
I own an enermax galaxy 1000 watt. Bought one just after they came out. Its quiet. Great psu. I needed it for a dual opty set up that has 2 independent cooling loops. The mobo requires 645 watts alone, not including my x1900xtx & 8 one gig sticks of ram + 7 hard drives. Its a work horse, but showing its age with games like CnC3. The optys are only 2.4 ghz and don't compare to the C2D at all anymore.
 
I wouldn't mind spending more money if a bigger PSU would let me expand, but the p180 case doesn't really have the room (I don't want it to be too crampt). Plus, if I want back up, i'll do it another way. I also plan on building a cheap c2d network server sometime in the future, so I won't need to do much more than drop 1 extra hdd in this computer when I need it.
 
I do a lot of codec conversions for both audio and video, i compress a lot of video and some audio (though the audio doesn't give me problems at all) plus I play games and run stuff like SETI and another program ( i forget the name) to do cancer research while I am at work actually doing cancer research, LOL. On top of that, I game and multitask (though multitasking doesn't need a quad).  
 
I want to be future ready, and the quad + a high OC will help.

Oh yeah, I can get an x1950xt cheaper? I own my x1900xtx, so that means they'll pay me to take the x1950xt away? NOW THATS A DEAL! Sign me up!
 
Btw, My original plans were to get a penryn, but after comparing price vs performance, I couldn't pass up th Q6600 w/ G0 on a cooling loop. Plus I haven't OC'd in a LONG time. And by long, I mean, OCing w/ jumper pins on the mobo. I might only be 22, but I've been messing with computers since 386s (i'm too young for 286s ). It'll be a new experience to use software instead of hardware for a change.