My first build, need opinions.

[Skambo]

Case: Cooler Master Storm Enforcer ( already bought )
CPU: Intel Core i5 3570k
Motherboard: Haven't decided if I should go with Gigabyte GA-Z77X-UD3H or ASUS P8Z77 LK ( little bit cheaper ) or I could get the ASUS Z77 Pro3 which would be more cheaper.
RAM: G skill 4gb ( already bought )
Hard drive: Using my other PC's.
DVD drive: Using my other PC's.
Power Supply: XFX PRO550 Power Supply
GPU: If I go with Gigabyte GA-Z77X-UD3H motherboard I would be able to get the 6850 but if I go with ASUS LK I would be able to get the 6870.
CPU Cooler: Cooler Master Hyper 212+.

Help me decide on the Motherboard and GPU and post your opinions please .
I can only buy the computer parts from Amazon because I got a gift card there.
I'm planning to play games on med-high settings and overclocking to 4ghz.

 

[Skambo]

Can anyone please post, I need to order these ASAP.

 

[g-unit1111]

That looks pretty good actually. Go with the Gigabyte UD3H - which is the same board I have but I realized that all the ports on it are USB 3.0. The Asrock Z77 Extreme 4 is also another good choice. Definitely get the 6870 - it's a far better option than the 6850.