New system build
 
XFX nForce 790i Ultra SLI Motherboard  
 
Asus Rampage Formula Motherboard

ASUS would be my choice!

Probably ASUS. XFX makes good video cards but not the best motherboards (quality, OCing wise). Also is SLI necessary? What's the rest of the specs?

SLI isn't a big deal, spec well haven't decided yet wanted to start with a good board and go from there

Budget?

With the rampage you will have a very good base for a awesome computer, just make sure your other components are as performing, also there's no point in getting such a good board without OCing it

what cooler should I use>?
 
 
Have Cosmos 1000 case

depends, how much will you be overclocking, TRUE or IFX-14 should do the best job for high OC

How about this? Xigmatek HDT-S1283
 
It's currently #2 at Frostytech
See: http://www.frostytech.com/top5heat [...] ELHEATSINK
Goes on Newegg for ~$35

Consider this board:
http://www.newegg.com/Product/Prod [...] 6813128336
X48 board with bios designed specifically for overclocking, supports features like loadline calibration. Massive copper heatsinks, runs cooler than Asus's x48. All solid capacitors last longer and provides more stable power flow, especially under overclocking conditions. 2 bios, if you corrupt one while updating bios, the backup will take over, and you're not screwed.

Memory support "ddr2 1200," not "ddr2 1200(O.C.)" as in Rampage Formula.
http://www.newegg.com/Product/Prod [...] 6813131284

Gigabyte's second generation DES perform better than Asus's first generation EPU:
http://www.tweaktown.com/articles/ [...] index.html
Although it's not as if you want a high performance motherboard for the power savings anyway, but it's still a plus. The more important part is DES provides stable power flow, thus avioding errors cause by Asus EPU.

Pick one of those for cpu cooling:
http://www.newegg.com/Product/Prod [...] 6835887011
http://www.newegg.com/Product/Prod [...] 6835233003

^Agreed. But, imo X64 is over kill considering that Nehalm is just around the corner.

What's x64?

^ correction i meant X48

Should I wait fo the Nehalm Boards?

Nehalem will be released at the end of this year, if Intel don't delay further.

Asus Rampage Formula Motherboard with IFX-14 cooler
 
Q6600 or save 2 week for the 9770 want to oc forsure

still can't decide on which to get, both has there pros and cons.
 
asus DDR2  
 
790I  DDR3  
 
leaning more towards asus for the DDR2 Friendly OC nub like myself.  
why is the ausu higher in price than the 790i? since it doesn't support DDR3?

Because Asus is Asus. You're paying more for brand name.

I know it's strange, since ASUSTek is a company based in Taiwan, with factories in mainland china, and people usually don't associate Made in China with good quality. But they made a name for themselves, so they can charge more, and people will still buy it.

Aside from that, x38/48 overclocks better than 790i.

Asus price is bad for reference, since it's inflated. A x38 board should cost around $200, a x48 should cost around $230.

^Agreed. But ASUS dose have very good quality (imo)