IMO drop the Mobo to the P8P67 Pro, and allot the $70 to something else.
Honestly, a 6950 for you is perfectly fine. Skyrim would be the game that needs the most power out of the three, and the 6950 should run it fine on 1080P. Especially if you unlock it to a 6970.
With dual cards, you get better per/$ for the most part, but lose out on upgradability and have to deal with little problems like profile optimization, increased heat, less space, etc. Since you plan on upgrading, a single semi-powerful card should be better for you. Though the $300 6850/gtx460 1G CF/SLI comes dangerously close to a 5970/580.
Finally, Premiere Pro's MPE does utilize CUDA, though even if you go AMD, you should still be able to enable a bunch of OpenGL accelerations IIRC. So unless you're serious about video editing, you'll barely notice a difference. Besides, CS6 apparently switches to OpenCL.