Do you already have the 2500k?
Are you going to use your Antec 900?
Okay so motherboard:
Solid overclocker and good on features. If you don't plan on getting Ivy Bridge when it's released, then there's no reason beyond the good looks to get the Gen3 version.
Those boards non-overclocked RAM standards are 1600
Any of those should do; just pick the ones you like the looks of and that have the lowest timings on them that you can afford.
Any of those video cards is a great deal, as you can partially flash it to a 6970 and a single one can play BF3 on recommended settings.
That power supply should be able to handle your 2500k and two 6950's. If you're paranoid about it you can
check this: http://www.overclock.net/power-suppl...l-release.html
or get the x750/x760 version of the Seasonic power supply.
If you would like to find a cheaper power supply that will still fit your needs check here:
I love my seasonic, by the way.
All of that works...if you're still using the 2500k you have now and the case you have now. Otherwise we might have to rework a few things...
Best of luck