They are the same CPU. The only difference is the 965 is a factory overclocked version. If you feel comfortable about overclocking then get the 955 and save the money, but if you don't want to OC, then go ahead and the get the 965. There is very little perfomance difference though... You will see no difference in games, and if you do it will be by a few FPS.
And don't get a AMD six core... I have several reasons
, if you are interested i can link you to my unfinished site (Webs.com because im poor and i dont have time to write HTML haha). If you really want performance then go for the I7 930. I have a list of CPUs on the site too (Pretty much accurate) that lists them in order of how powerfull they are.
So i would get the Intel I7 930 since it is only 288 (From the 300 for the 920), but if you don't have the cash then go for the AMD OR the Intel I5 750. My reasons are because of how far AMD is going down in price and Intel isn't, then i would stick with the AMD.
if you want that link (Or anyone else) i ll link it here! (It is in its baby stages so i think there a few missing CPU's and there are several out of order...