i have a x4 945 at stock and im thinking upgrading to a x6 and i cant use fx cpu in my board they are no supported (ga-ma770t-ud3p) i render videos with pinnacle studio 17 and play the some of the newest games so thats why im asking ?
From I've Googled, it seems Pinnacle Studio 17 doesn't take advantage of extra cores, so the drop in frequency might actually harm performance rather than help, so you might want to get a Phenom II X6 1100T. Though, personally, I'd get a nice aftermarket cooler and OC your X4 945 in this situation since a new CPU seems like it wouldn't be worth the cost.
i have 8gb ddr3 1600mhz and would a B75 Pro3-M and a i7 2600k or i7 3770k be good ?
You will want a Z77 board if you go with those chips. B75 cannot overclock. A B75 with a Xeon 1230 v2 would work, and cost less, though. Even a 1230 v3 or 1240v3 or 1245v3, if you wanted integrate graphics, haswell Xeon with a B85 board would be cheaper than a 3770k. Actually this combo is cheaper than getting the 3770k by itself.
If you don't want to overclock, then a Xeon combo is the most cost effective solution if you go with an Intel build. It looks like you already are using a dedicated GPU, so you will definitely have to reuse that.