4pin or 8pin connector with p6n diamond and E6750 core 2 duo?!

hi guys my system boots up fine and everything is working but i am using one 4 pin connector from my psu connecting it to my motherboard

the psu also has another 4 pin connector , shall i connect this to the second blocked connector on the motherboard or is one 4 pin enough?

edit: the motherboard by default has an 8pin connector however out of the box there is a plastic piece on 4 of them so that only 4 show but this can be removed.

e6750
msi p6n diamond
ocz gameXstream 700W
8800gt

my rule of thumb is if mobo has got a socket and the psu has the plug to fit it...fit it :)