6950 or 7850 ?

Hi , i'm thinking about getting a new GPU , and I was thinking about gettinh either a Sapphire 6950 2GB Dual Fan Version , or a XFX 7850 2GB . The 6950 is 190€ and the 7850 is 245€ . I've seen some benchmarks and I think that it isn't worth my money , but what do u think ? BTW , I will also need a new PSU , so what do u recommend (The cheaper , the best ) ?

XFX HD 7850
Sapphire HD 6950


My Pc Specs :

i5-650 3.3Ghz
6Gb Samsung DDR3 1333 Mhz
GT 330 ( OEM )
WD 1TB HDD
Cheap piece of *** "450w" PSU

Thanks for your time