It doesn't as they don't make a K i3 lol. It really isn't needed though. I ran my 3960x stock for the longest time, and currently since my switch to 8 pro full time my i5 750 is stock too.
My 6000+ and 5850 played BF3 well on ultra with no AA.
An IB i3 is like 3x the speed of that old 6000+. Not to mention, an i3 has HT so 4 threads. But yes to answer your question a dual core is perfectly fine. You have to wait for next gen console/games before they really start taking advantage of multi-core CPUs. Even still that's a 50/50 as well.
Yes of course, and if you get a 77/75 board you can always upgrade to a quad later if you have more free cash.
Edit: Currently playing Mafia 2 and tried my 750 in dual core mode with a 580 and maxed out it's fine. It's the only game I have installed right now though.