Should I change AthlonX2 6400+BE with Phenom II 965?

I'm not sure if I should change my Athlon X2 6400+ with a phenom II 965 BE.What I mean is I mostly play games with my system,and I wanted to know that changing my CPU will have any impact on games or not;And if it does,how much I should expect?Also I should mention that I play in 1920x1200 resolution.The only thing that bothers me with my current CPU is it's heat,it's being unable to overclock(Can you believe a 100Mhz OC for a black edition CPU?I've tried everything,it just doesn't stabily OC),It's power consumption for a dual core CPU and etc...

My system specifications:

Mainboard: Gigabyte MA780G-UD3H AM2+(140Watt CPU supported)
CPU: Athlon X2 6400+ Black Edition @3.3Ghz
CPU cooler: Cooler master air cooler(I don't remeber the Model!!!)
Case: NZXT Tempest
RAM: 2x2GB UMAX DDR2800
Graphic: Sapphire radeon 5850 1GB DDR5
HDD: 2500 GB(500+500+1500 non-raid)
Power: 600 watts real

Well most games are GPU-limited but getting a X4 965 will give you a boost in games which benefit from a faster CPU like HAWK,GTA IV and some RTS games.
Also it will give you a boost in apps like PhotoShop,3D rendering etc.
So if it doesn't cost you much,go for it IMO

http://www.anandtech.com/bench/def [...] &p2=88&c=1

This shows a Athlonx2 6400+ vs PhenomII 955 stock speed, scroll down to see the game comparison, as i see it you will gain in everything. I would go for it if i were you.

Yes it will give you a good boost in performance.Those were some of the improvement it will bring,check Toms CPU charts too

Not to bash Toms, but I think anandtech's bench tool is very good. They should take hint and make something similar or improve upon it.

Thanks for your answers,but I was wandering if CPU has so much impact on high resolutions,considering my setup(1900x1200),and also how much difference it will cause,considering the move from 3.2 Ghz Dual core athlon to 3.2 Ghz Phenom II quad core.I know in clock for clock comparison phenom II is much more faster,but what about the resolution I mentioned?

And I'd appreciate if you have any alternative suggestion besides 955 BE and 965 BE considering my configuration...

As i said there are some games which benefit a lot like GTA IV,Prototype,some RTS games and more.
Well my recommendation would be either 955BE or 965BE in AMD CPUs,other alternatives would be Core i5/i7 but with intel you need to change your motherboard and RAM too

6400 won't overclock any further because as zipzoomflyhigh mentioned, it's already maxed out. It's an old K8 90nm processor, it just has no head room left. It would be like AMD releasing a 3.8Ghz C2 Phenom II when very few could even hit 4.0Ghz stable. lol

I personally would recommend the upgrade to a Phenom II X4, but go for the 955 if your gonna overclock, it's the same as the 965 only cheaper.

But even at 3.3Ghz dual core, I think it should be pretty decent even for 1920x1080 gameplay. The only problem that might hold up the gaming if ever will be the lack of L3 cache but try "ebooster" and assign some of the RAM capacity as extra cache.