I think you should wait for the next round up, it shouldn't be too long until they release another new graphics card. Might be a couple of months but it is probably worth the wait for newer technology
Good cards, though I would prefer the 4870 if you weren't already on an SLI motherboard!
Just as a matter of interest, do you do any overclocking on your CPU and if so, what is the maximum stable clock you've had?