Which system should i go with?

[SOCA1]

Mainly gaming at (1920x1080p), and yes I am on a tight budget around $650.
SETUP1:
CPU: Fx-6300
GPU: Sapphire Radeon 7870
MOBO: GIGABYTE GA-990FXA-UD3
PRICE: $645 (including ram and psu these are the same for every setup)

SETUP 2:
CPU: Phenom iix 4 965 BE
GPU: Sapphire Radeon 7950
MOBO: ASRock 990FX Extreme3 AM3+
PRICE: $650

SETUP 3:
CPU: i5 3570k
GPU: Sapphire Radeon 7870
MOBO:ASRock Z75 Pro3 LGA 1155
PRICE: $670

I am only gaming a 1080p on one monitor so is the 7950 overkill?
Oh and if the ram and psu is important i am using 8gb g.skill (2x4) ($65) and a corsair builder series 600 watt ($60).

Thanks for any advice!

 

[ScrewySqrl]

if you change the 6300 Mobo to a 970, you can probly change the 6300 to a 7950, which would make it the best overall.