I agree that you should hold off until the new hardware. Intel's P55 chips are better than the phenom II x4's, so sandy bridge will be even better. Phenom II X4 + 2 GTX 570's is going to bottleneck your graphics performance like Mr. Pizza said.
Yeah, if your not gonna run an intel CPU with that build, then maybe a nice x6 Black Edition AMD CPU, but think two 570's are overkill, but it depends on what your playing i guess. Even two 470's would do the job, just as well if not better, IMO, maybe 480.
Anyways its up to you in the end.
If you're willing to spend the money and up the processor to a x6 AMD or some sort of HIGH END i5/ Any i7 then get both 570's, if not then just drop it to x2 470's or a 480 ( you could SLI if you want )