The problem with all of these is a lack of information.
For what resolution monitor?
For what purpose? Is this meant to be a LAN party system or a dorm system?
All I can do here is try to hit the highest frame rates possible and ignore other considerations, as that is most likely to garner the largest votes.
EVGA P55V 120-LF-E651-TR LGA 1156 Intel P55 Micro ATX $75
http://www.newegg.com/Product/Product.aspx?Item=N82E16813188064
According to EVGA, this is a true x8/x8 SLI board
i5-655K $200
http://www.newegg.com/Product/Product.aspx?Item=N82E16819116369
Easy to OC. Most games still benefit little from more than two cores, and these two cores can be pumped up pretty high. In the tradition of these builds, I'm not building for tomorrow, but getting the best performance for the buck today.
ZALMAN CNPS10X Performa $50
http://www.newegg.com/Product/Product.aspx?Item=N82E16835118059
Top performance. 6 inches high. Obviously won't fit in many mATX cases.
TX-2 $5
http://www.newegg.com/Product/Product.aspx?Item=N82E16835154003&cm_re=TX-2-_-35-154-003-_-Product
Mushkin Blackline DDR3 1600 CL7 $95
http://www.newegg.com/Product/Product.aspx?Item=N82E16820226103&cm_re=DDR3_1600_4GB-_-20-226-103-_-Product
I could have saved some here, we all know by now that RAM is not a big factor. However, I thought this a safe buy because it will end up overclocked if the CPU is pushed like it should be.
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Silverstone TJ08-B $100
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163058
This case will take larger CPU coolers and longer cards. Not many mATX cases will do this. It looks nice too.
Antec TP-650 $100
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371021
All needed connections, modular, 80plus bronze, well reviewed.
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2 x ASUS ENGTX460 DirectCU/2DI/1GD5 GeForce GTX 460 (Fermi) 1GB $460
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121391&cm_re=gtx_460_1gb-_-14-121-391-_-Product
Good cooling. Good voltage regulation. Probable overclock.
WD Caviar Black 750GB $60
http://www.newegg.com/Product/Product.aspx?Item=N82E16822136283&cm_re=Caviar_Black-_-22-136-283-_-Product
Warranty, reliability, price per GB.
Sony DVD drive $18
http://www.newegg.com/Product/Product.aspx?Item=N82E16827118039
$1163 before rebates and shipping.