I suggest several changes. First off, wait for Cayman, the 6950 should be coming out in 8 days with a decent availability (says Fudzilla) Also it should cost 350$ only a little more than the 6870 for almost 40% performance increase. So that's one thing, wait.
Also, Sandy Bridge is coming out soon, doing this upgrade would be a waste. And from the looks of your parts, it doesn't look like you have a small budget, about 800$. You could do an SB upgrade.
The 955 would be a better choice, the 1090T isn't worth the cost, the i5 750 beats it out in many benchs at a lower price (190$) The 955 is just enough horsepower to handle most modern games. I play BFBC2 with my system (in the sig it has 955) perfectly fine, with my GPU OC'd to 1000/1205 I play BFBC2 at the Highest settings and get practically no visible lag.
o.o Okie dokie, then don't get the 965, the 965 is basically a 955 with a higher stock clock. But you really won't see a difference. Go with the 955 it's about like 10-15$ cheaper than the 965. Plus it's just as good, it'll OC to 4.0ghz if you plan to easy. As for your motherboard, if your low on money, don't get that board. I suggest saving 45$ and getting this Asrock 870 Extreme3. It's just as good with the same USB 3 and SATA 6. Plus it's pretty great.