you have a solid PSU, you said it's working fine and its proven you have plenty of power to run your system. you will be fine.
here is a review of the 600w version where they pulled 712w off the unit before its safety precautions kicked in (always a good thing). the 700w uses the same platform 600w.
The new StealthXStream 2 600 W really surprised us. It achieved up to 87% efficiency, with numbers that would easily qualify it for the 80 Plus Bronze certification, even though it carries only the standard 80 Plus. Voltages were always very close to their nominal values (3% regulation), and noise and ripple levels were very low at all times.
We could pull up to 712 W from this power supply with efficiency still above 80%. So you buy a 600 W power supply and get a 700 W.