I'd grab the 1055t. You COULD go with the 960T, but those two extra cores are not always going to unlock, much less work (esp if ur OC'ing).
I've had the 1055t since it came out and I can get mine up to 4.4Ghz at 1.65v and I've been running it at 287*14=4.02Ghz 1.45v for about a year and a half, since launch with no problems at all.
The 1090BE or 1100BE MAY OC higher and the do have an unlocked multiplier, but that's no garantee that they will reach a higher OC at all. It's just another way of getting to the same place.
If you're really going to drop that kind of cash on an AMD CPU right now, I'd spend the $150 for 1055t and that way at least you'll KNOW you're getting six working cores and I'm telling you that AMD's manufacturing for those chips is SO Mature, that you'll most likely get just as good of an OC out of it as you would a more expensive model.
Personally, I love AMD and my 1055t at 4ghz is plenty for anything I can throw at it right now, but I must admit. If I had to build a brand new system right now, I'd have to go with Intel. Even though a 2600k would cost about $200-$250 more than a 1055t build (w/mobo and CPU), I'd say the OC potential of the Intel chip along with single core performance per mhz anyway would justify the price...to me anyway.
Good luck, either way you go.
BTW, you COULD sell your CPU on eBay and mitigate your cost. Just like "Best Answer" said though, I wouldn't do it if your only concern is gaming. Now, if you're doing video manipulation, 3D rendering or unziping a lot of files using 7zip, etc, aka highly threaded apps..then it might be worth the 50bucks or so that it would cost you after selling your current 4 core.