There is no reason not to go for the 670 if you are able to get it. The FX-4100 will bottleneck slightly, but I would recommend OCing it just a bit more in order to get the most performance. The bottleneck will probably be very minimal, so there is nothing very little to be worrying about.
i cant afford a good cpu cooler and a gtx 670 to oc my cpu. So i am going to let it on 3.9 stock. If i go for the gtx 670 what psu needed for that card ? i have a 650w
A 650 Watt is fine, just make sure that it is a reliable brand such as Corsair, Antec, Seasonic, OCZ,etc. If you cant afford a CPU cooler than no problem. I am just telling you not to expect Ultra settings on BF3 (VERY CPU heavy game). Other games should run fine.
Well i live in europe greece and here the prices are very high. The gtx 670 goes around 600$ here and the coolers like 80$ so its hard to go full upgrade. So thats why i am trying to find a mid solution for the better perfomance. the games that i mostly play are gw2 league of legends and counter strike. But now i am forward something like bf3 dishonored etc . So if i go for the MSI N660TF 2GD5/OC 2GB (gtx660) ill be fine ? and then just ad some more ram or put an ssd...