If you're going to spend 2k, you might as well go the i7 route and the 1366 chipset, which is better for OC'ing, performance, on board features like USB 3.0, SATA3, eSata for some boards.
If you live near a Microcenter, the i7 is $199 in store pick up, and you could get the GA-X58A-UD3R for $209. = $409
Otherwise if you're set on the i5, just swap the MOBO / CPU / RAM with what's listed below.
i7 930 + asus p6x58d-e combo - $489.99
http://www.newegg.com/Product/Comb [...] mbo.428205
or
i5-750 + ASUS P7P55D-E Pro $339.98
http://www.newegg.com/Product/Comb [...] mbo.427752
Case - CM 690 II - $89.99
http://www.newegg.com/Product/Prod [...] -_-Product
Depending on your preference, or if you want somthing more high end, there are lots of case to choose from, how much are you looking to spend on a case?
Stick with
2 x GIGABYTE GV-R583UD - $420
PSU + RAM combo: ( $35 savings )
1. CORSAIR HX Series CMPSU-650HX ( -$20 Rebate )
2. CORSAIR XMS3 6GB (3 x 2GB) 1600c7
Combo Price - $274.98
http://www.newegg.com/Product/Comb [...] mbo.407536
ASUS VW266H Black 25.5" - $299
http://www.newegg.com/Product/Prod [...] S%20VW266H
HDD - SAMSUNG Spinpoint F3
http://www.newegg.com/Product/Prod [...] 6822152185
HS - Scythe SCMG-2100 Sleeve CPU Cooler - $35
http://www.newegg.com/Product/Prod [...] -_-Product
i7 Grand Total - $1608
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To answer your question - i5 boards do not support tri-channel, they operate off Dual Channel mode.
That's why on the i7 builds, the Ram is always 6GB ( 3 X 2GB ) , 12GB ( 3 x 4GB )
On the i5 u're looking at 4GB or 8GB