choosing final componentes for Build

Solution
This is cheaper than your original build but much faster due to improved GPU. The motherboard you chose does not support 2 GPUs. Your choice is good and I don't recommend a system with 2 GPUs unless you have 3 monitors. I created two killler builds cuz the 7870XT is hard to find, cuz everyone wants it.
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3350P 3.1GHz Quad-Core Processor ($179.99 @ Newegg)
Motherboard: Asus P8B75-V ATX LGA1155 Motherboard ($84.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($49.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive...
The mainboard has a built in Ethernet controller so as long as you have internet connection your board will support it. And I would agree get a better GPU if you can afford it. The GTX 660 is on the low side for a gaming rig but if the GTX 660 is all you can manage you can always add a second one later on and do SLI to give your system a boost.

I would keep the PSU because if you go with a SLI setup later on you might need the extra power.
 
This is cheaper than your original build but much faster due to improved GPU. The motherboard you chose does not support 2 GPUs. Your choice is good and I don't recommend a system with 2 GPUs unless you have 3 monitors. I created two killler builds cuz the 7870XT is hard to find, cuz everyone wants it.
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3350P 3.1GHz Quad-Core Processor ($179.99 @ Newegg)
Motherboard: Asus P8B75-V ATX LGA1155 Motherboard ($84.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($49.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($79.99 @ Newegg)
Video Card: Sapphire Radeon HD 7870 XT 2GB Video Card ($249.99 @ Newegg)
Case: NZXT Phantom 410 (Black/Orange) ATX Mid Tower Case ($87.98 @ Newegg)
Power Supply: SeaSonic S12II 520W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($70.98 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($24.98 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($105.98 @ Newegg)
Total: $934.87
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-04-18 04:55 EDT-0400)

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3350P 3.1GHz Quad-Core Processor ($179.99 @ Newegg)
Motherboard: Asus P8B75-V ATX LGA1155 Motherboard ($84.99 @ Newegg)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($49.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($79.99 @ Newegg)
Video Card: Galaxy GeForce GTX 660 Ti 2GB Video Card ($284.98 @ Newegg)
Case: NZXT Phantom 410 (Black/Orange) ATX Mid Tower Case ($87.98 @ Newegg)
Power Supply: SeaSonic S12II 520W 80 PLUS Bronze Certified ATX12V / EPS12V Power Supply ($70.98 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($24.98 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (OEM) (64-bit) ($105.98 @ Newegg)
Total: $969.86
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-04-18 04:57 EDT-0400)
 
Solution


BTW. Once you make a build on the partpicker website then click on "BBC Code Markup" and select "Your Preferred Merchant List" then Ctrl+C to copy it and go to tomshardware and paste