I7 or Core 2 Duo? under $1500 total

Well for $1500 budget, you should be able to get a i7 setup easy...
you should have posted this thread in the
"Forum > Homebuilt Systems > New System Build >" to get much better responses...
And do check out this sticky before you post it...
*How To Ask For New Build Advice*
http://www.tomshardware.co.uk/forum/page-261222_13_0.ht...

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $74.99
COOLER MASTER RC-690-KKN1-GP Black SECC/ ABS ATX Mid Tower Computer Case - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $119.99 ($99.99 after $20.00 Mail-In Rebate) Free Shipping*
CORSAIR CMPSU-750TX 750W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply - Retail

http://www.ewiz.com/detail.php?name=MB-EX58U3R $185.99 | $170.99 after rebate Free Ground Shipping
GIGABYTE GA-EX58-UD3R Core i7/ Intel X58/ DDR3/ CrossFireX/ A&GbE/ ATX Motherboard

http://www.ewiz.com/detail.php?name=I7-920 $265.99 Free Ground Shipping
Intel Core i7 Processor i7-920 2.66GHz 8MB LGA1366 CPU, OEM

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $39.99 Free Shipping*
XIGMATEK Dark Knight-S1283V 120mm Long Life Bearing CPU Cooler - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $7.99 Free Shipping*
ARCTIC COOLING MX-2 Thermal Compound - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $249.99 ($229.99 after $20.00 Mail-In Rebate) Free Shipping*
EVGA 896-P3-1170-AR GeForce GTX 275 896MB 448-bit DDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $249.99 ($229.99 after $20.00 Mail-In Rebate) Free Shipping*
EVGA 896-P3-1170-AR GeForce GTX 275 896MB 448-bit DDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $94.99 Free Shipping*
G.SKILL 6GB (3 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Triple Channel Kit Desktop Memory - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168... $24.99 Free Shipping*
LG Black 22X (CAV) DVD+R 8X DVD+RW 16X DVD+R DL 22X (CAV) DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 22X DVD±R DVD Burner - OEM

http://www.newegg.com/Product/ComboDealDetails.aspx?Ite... Combo Discount: -$20.00 Combo Price: $149.98
Western Digital Caviar Black WD6401AALS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Hard Drive - OEM
Microsoft Windows Vista Home Premium SP1 64-bit for System Builders - OEM

Total: $1,469.88 | $1,394.88 w/mail in rebates

^ Nice setup...
2 GTX 275 ??? is that a typo ???  

Another good RAM with CAS 7...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

But that mobo doesnt support SLI out of the box...
Its BIOS has to be updated ...
http://www.tomshardware.com/news/gigabyte-nvidia-sli-mo...

^
Ok I would change a few things.

First of all just get everything from Newegg, they are easier to deal with if there is a return.

ALSO, the CPU above is an OEM chip which means it is the the CPU only, which doesn't matter since you are buying a cooler, but will only come with a 90 day warranty (i think, or whatever the OEM, ie website, offers). The Retail boxed chips come with a 3 year warranty from intel, It's worth the extra $15 to have that assurance.

Next, That mobo does not support SLI. Nvidia licenses SLI support and if that model board was not licensed for SLI, you won't get it. I wouldn't rely on the "Cheat" BIOS flash, because what if an update is needed in the future and the cheat no longer works you are screwed? I'd stick with one of the below boards.

ASUS P6T: http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Gigabyte UD4P: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Sorry, this one supports SLi for $209.99 or the Asus P6T is good too.

GIGABYTE GA-EX58-UD3R-SLI LGA 1366 Intel X58 ATX Intel Motherboard - Retail

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

^-1
don't do trifire, if anything, go dual 4890 over 3 4770's