wao.. these replies cleared my mind. Thank u all .. I got the point of not taking 4670. and I didn't know x16-x4 CF is useless.
And about 750W requirement, Sapphire's oficial page, MD comp's details page, everywhere it's mentioned like that.750W.
If I am not CFing, then I think 620seasonic(80plus bronze) is best.
between,MD comp did not process my payment for sapphire dual x r9 280x as it just went out of stock. So I will go with the asus one.