Building a new system... need help!

[Static EMP]

I am building a new system, and I need to know what I should go with for some of the parts.

Processor: Duo E6850 or Quad Q6700? The rig is mainly for gaming, but I do some encoding here and there (not a ton), and do run Photoshop a bit. I know they say Duo is better for strictly gaming, but will that only last for a bit? Will Quad Core take over in the future for both apps and gaming?

Motherboard: nForce 680 SLI or Intel X38? Is SLI even worth it? The performance increases never looked like it warranted the extra dough. And if I get X38, i can use DDR3 SDRAM. What will give me the better performance: the ram or the nvidia chipset?

Cooling: Right now am thinking of a PC Power and Cooling 750w. My main issue is I don't know how to calculate how much power I need -- theres going to be the equipment mentioned above, an evga 8800 gtx, a sound blaster card, two 500 gb sata hard drives, and a dvd-rw for now.

 

[sutahz]

True, dual core has been shown to out perform quad core in gameing, but its not a huge difference so I would go w/ the Q6600.

I'm sure someone else has a more knowledgeable responce for this, but the 680i is a more mature chipset. You'll just have to look at some reviews of 680i and X38 boards to see which you like better. DDR3 i so expensive though, but you can get X38 boards w/ DDR2. As for SLI, you can get hacked SLI drivers for the P35 and X38 chipsets I believe.

A link to a power calculator (don't know if its the best though):
http://educations.newegg.com/tool/psucalc/index.html

I wouldn't get a 8800GTX though, unless money is not a factor. Go for a 8800GT, the new 880GTS (G92) outperforms the GT by 10% but costs 20% more. Even better, wait for the 8900GTX or if you can, wait for the 9000 series of cards. But today, I would highly recommend the 8800GT 512MB.
Do you already own the 2 500GB hdd's? If not may I suggest you buy a WD7500AAKS, this hdd really has a great price/performance ratio. You could also look into the Samsung F1 750GB hdd, I'm sure its very nice as well.

Thats my take on your situation (save money, get DDR2 and a 8800GT).