Being that your processor is a quad core, if you overclocked it you probably wouldn't see much bottlenecking. I checked out your mobo and it looks like it has good overclocking capacity as well so I think you would be fine to upgrade to and 69XX series video card.
Thanks for the Quick reply, I've not had much OCing xp but from what I've read on this site I'm pretty sure I've got it down.. only problem is tweaking voltages and unwarranted fear of damaging hardware.
I've got the 3 reccomended programs for OCing Prime,realtemps,CPU and GPU-z.
Only thing left is to suck it up and get on with I guess - I'm thinking a 6970, so when I actually upgrade to a new CPU/Mobo I can crossfire with a 2nd one.