$1000 New Gaming PC

Hey guys, I'm going to build my own computer for the first time, I have a basic idea of what I'm going to buy, but I'm stuck between the Radeon 7950 and the GTX 670. Also, any suggestions on a 120hz monitor?

Approximate Purchase Date: This Week
Budget Range: $1000 (Not including OS, peripherals or monitor)
System Usage: Gaming
Monitor: Yes, 120hz
Parts Preference: GPU - GTX 670 or Radeon 7950 (I prefer MSI so maybe 7950 Twin Frozr III or 670 Power Edition)
Overclocking: Yes
SLI/Crossfire: In the future
Monitor Resolution: 1920x1080

Additional Comments: I can't decide if I should get a GTX 670 or a Radeon 7950. I want to get the MSI 7950 TFIII and then overclock it so that it outperforms a GTX 670 and I know it is possible. The 7950 is also cheaper. But from the benchmarks I've seen, they only compare a 7950 Overclocked with a stock 670 so I don't know how a 7950 overclocked performs against an MSI GTX 670 Power Edition +overclocking. Also, the GTX 670 has Adaptive V-Sync, TXAA and PhysX. Adaptive V-Sync I can sacrifice because I am getting a 120hz monitor and I won't be using V-Sync often. TXAA also makes things smoother and PhysX also adds the cool particle effects and such, but are those two worth the extra price increase? I'm going to be playing Medal of Honor: Warfighter, Black Ops 2, Far Cry 3 and Crysis 3, do those games use PhysX? I guess we can't speak for Crysis 3 because it's not out yet, but it does use CryEngine 3 right?

Here's my basic idea:

CPU: Intel Ivy-Bridge i5-3570k (going to overclock it)
CPU Cooler: Cooler Master Hyper 212 Evo (for overclocking CPU)
Motherboard: Asrock Z77 Extreme4
Memory: Corsair Vengeance 8GB (4x2) DDR3-1600
Storage: Western Digital WD Caviar Blue 1TB 7200RPM 64MB Cache
PSU: Corsair Enthusiast 750W ATX12V / EPS12V
Optical Drive: Some 24x DVD Burner
Case: NZXT Phantom 410 (Black)
GPU: MSI GTX 670 Power Edition or MSI Radeon 7950 TwinFrozr III