I have a similar situation. Core i3, and probably getting a Radeon 6950 1GB soon. I want to play at 1080p though, and also plan on upgrading next year to either i5 or i7 Sandy/Ivy bridge, depending on the price/performance ratio.
I've been told there shouldn't be a big, noticeable bottleneck, specially if you OC, so you'll be fine, and if you got the 6870 at the end, you can simply forget about any issues like these
@shrkbay: interesting, new HDs coming out soon? Did you see any details about their price or performance?