I run that set-up already. You'll loose frames on the P67, so the X58 or wait for the X68 Q4 2011. With bezzling 5900+x1080 is a saturation problem on x8/x8.
If you cannot wait, and can live with 5~10 FPS loss then P8P67 DELUXE or Maximus IV Extreme or GA-P67A-UD7 or EVGA P67 Classified when released. In gaming, clock per clock, the i5-2500K vs i7-2600K is negligible.