Thanks for the inputs.
I have confirmed that 6-pin to the GPU is connected correctly. And since I am not going to OC as of now (and when I do, I anyways plan to take a corsair branded PSU), I felt the 4-pin eatx would be sufficient. But I will think about the 8-pin factor too.
I have PSU from my old PC, but again that also has only 4pin eatx connector.
I am unable to get old of any X2 AMD processor and hence cannot check with that.
I am left with only choice of taking it back to the dealer and ask whether he has tested with similar rig (as he suggested the PSU for me

)
But before doing I thought of putting out my query here to see if anything else I am missing.
Currently I am situated in Bangalore