It's way too early to be starting a thread on here for a build planned in December. You want to start your build thread a week or less before you plan to buy. There's the new PCI-E 3.0 generation cards due out around December that will be supported by Ivy Bridge cpu's due out in April/May.
Here's what a single monitor build could look like if you were to do it today. That Corsair case just came out on newegg a few days ago and they come with everything but the kitchen sink. Multiple fan controllers, great cooling/ventilation, option to add more fans, dust filters, front USB 3.0 ports, etc...
http://www.newegg.com/Product/Product.aspx?Item=N82E16811139009 $129.99 - $114.99 after mail-in rebate card FREE SHIPPING
Corsair Carbide Series 500R Black Steel structure with molded ABS plastic accent pieces ATX Mid Tower Computer Case
or that same case but in white....
http://www.newegg.com/Product/Product.aspx?Item=N82E16811139010 $129.99 - $114.99 after mail-in rebate card FREE SHIPPING
Corsair Carbide Series 500R White Steel structure with molded ABS plastic accent pieces ATX Mid Tower Computer Case
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.732099 $683.98 - $35.00 Mail In Rebates FREE SHIPPING
CORSAIR Professional Series HX1050 1050W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS SILVER Certified Modular Power Supply
MSI N580GTX Twin Frozr II/OC GeForce GTX 580 (Fermi) 1536MB 384-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157269 $279.99
ASRock Z68 Extreme7 Gen3 LGA 1155 Intel Z68 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
http://www.microcenter.com/single_product_results.phtml?product_id=0354589 $179.99
Core i5 2500K LGA 1155 Boxed Processor
http://www.newegg.com/Product/Product.aspx?Item=N82E16835185168 $49.99 FREE SHIPPING
Scythe SCMG-3000 120mm Heat Pipe CPU Cooler
or this one due out on newegg any day now...
http://www.coolermaster-usa.com/product.php?category_id=1623&product_id=3049 $49.99
Cooler Master Hyper 612 PWM
http://www.newegg.com/Product/Product.aspx?Item=N82E16820233186 $52.99 FREE SHIPPING
CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Low Profile Desktop Memory Model CML8GX3M2A1600C9
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.696141 $67.48
$5 off w/ promo code EMCKAHH23, ends 9/28
ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - OEM
Seagate Barracuda ST31000524AS 1TB 7200 RPM SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148442 $196.99 FREE SHIPPING
Crucial M4 CT128M4SSD2 2.5" 128GB SATA III MLC Internal Solid State Drive (SSD)
Total: $1,641.40 *not including shipping, rebates, and promo codes
http://www.asrock.com/mb/overview.asp?Model=Z68%20Extreme7%20Gen3 <----- a better look at that board
http://www.asrock.com/microsite/PCIe3/ <----- PCI-E 3.0
http://www.tweaktown.com/reviews/4272/asrock_z68_extreme7_gen3_intel_z68_motherboard_review/index.html <----- review of that board
http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html <----- review done here on toms showing boards like the one above with the NF200 Bridge (dual cards @ x16 & x16) help to reduce micro stutter