Hello all, my older brother just built me a new gaming pc. He talked me into getting an Fx 4100 (bear in mind I had no idea how bad they were at the time). I am thinking whether or not a Phenom II x4 965 would be a good upgrade.
Well since you did not list any problems you are having with the FX-4100 it is hard to say. I can tell you that I went from a Phenom II 1090t to a FX-8120 and it was a very good UPGRADE for me. The item I would upgrade would be that "crappy" PSU! In all respects at least on my two AMD/ATI rigs going back to a Phenom II would be a downgrade as I had a few games that would give me a slight stutter on my 1090's that I do not get with the FX-8120 or FX-8150 rigs. If I had anything to do over I would have got FX-8120 for both rigs but that is really all I would have changed.
It'd be an upgrade, but hardly. You'd be much better off putting that money elsewhere, such as a new PSU or some more RAM. If you want to upgrade your CPU, hold off until Piledriver launches, as that'd be a much better option if it lives up to the hype.
To answer your last question, there are, but again you'd be paying more than you should for the gains that you'd see: Phenom II X6s are a similar architecture to the 965 (with an improved memory controller and better overclockability) and have 2 extra cores.