I never heard of gembird, so i guess its a cheap psu, that is probably not good.
I took a quick look and they seem to be around 30 dolars a piece, wich tells me its probably a bad unit
Do not get it buy a better branded one, (corsair antec silverstone, seasonic, xfx) 450W is plenty.
About the 6670 its not a bad card and may suffice your needs, and if you are on a budget the extra money you have to spend on the PSU may be a good way to save.
If you can the extra money for a 650ti or 7850 is a FAR BETTER card. Worth the money IMO