MY first computer build

[gta4master]

Hey guys,
I am replacing a alienware m14x and i want to know if this rig is worth the replacement
I have been shopping around a lot for different builds that I could make, and I think I finally got one that looks great
but I want to have a secondary opinion.
my budget is around 1000$ (can go up or down slightly)
These are the specs;
Case: Zalman Z11 Plus Mid Tower ATX Case Black 4X5.25 1X3.5 5X3.5INT No PS USB3.0
Motherboard: ASUS P8Z77-V LK LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS (Model:P8Z77-V LK)
PSU: RAIDMAX RX-600AF 600W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS BRONZE Certified Power Supply (Model:RX-600AF)
CPU: Intel Core i5-3450 Ivy Bridge 3.1GHz (3.5GHz Turbo) LGA 1155 77W Quad-Core Desktop Processor Intel HD Graphics 2500 BX80637I53450 (Model:BX80637I53450) /or an intel Core i7 3770K Unlocked Quad Core Hyperthreading Processor LGA1155 3.5GHZ Ivy Bridge 8MB Retail
RAM: G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-8GBRL (Model:F3-12800CL9D-8GBRL)
Hard Drive: Seagate Barracuda ST1000DM003 1TB 7200 RPM SATA 6.0Gb/s 3.5" Internal Hard Drive -Bare Drive (Model:ST1000DM003)
GPU: EVGA 04G-P4-3673-KR GeForce GTX 670 FTW+ 4GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card, or a GIGABYTE GV-N680OC-2GD GeForce GTX 680 2GB 256-bit GDDR5 PCI Express 3.0 x16 HDCP Ready SLI Support Video Card (will it work with the motherboard size and fit in the case and is it worth the extra money?)
Internet card: please make a suggestion.
DVD drive: ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X DVD Burner - Bulk - OEM
OS:Microsoft Windows 7 Home Premium SP1 64-bit - OEM
With this computer I want to run Gta 4 with icenhancer in multiplayer and Battlefield 3 at 1080p at high or above settings at a framerate above 60.

I will overclock the gpu it if i get it.
Tell me if there is anything I can improve on.
any criticism is accepted