OK.

Old machine had one GPU and pulled 570 khashes per second.

New machine has two GPU's, the primary gets the same 570 Kilohashes, but the secondary gets more (700)?

Am I reading that correctly?

I'd guess that what you're seeing is the overhead that windows is imposing. Your primary GPU runs your display, even if you're not doing anything with it, Windows is still probably reserving parts of the GPU for display effects, etc.

That's why the hard core miners run Linux without a GUI at all - that way every clock cycle of the GPU is devoted to mining insead of running a display that you're not looking at.

Or... maybe I misinterpreted, but I think that's what you described.