What psu for a 7950?

ASPEEDYNINJA

Honorable
Feb 14, 2013
90
0
10,640
im doing a new build with either a 7870 or a 7950 depending on how much i can get so i want the psu to be able to run the 7950. Would the xfx 550w be enough for my system? If not what should i get? i dont really want to spend more then £50-£55 ($75-$85) on the psi.

i will be getting either a 3470 or a 3570k depending on weather i want to overclock or not.
i will not be doing crossfire if i want to upgrade in the future i will just upgrade the card. Because im not doing crossfire is it worth getting an m-atx board?

thanks for any replies.
 

ASPEEDYNINJA

Honorable
Feb 14, 2013
90
0
10,640
thanks guy i should have mentioned that im probs gona get a 3570k thats why i was getting the msi board if i overclock my cpu will the psu still be fine?