ATI 4770 with new CPU

you should definatley see an increase its just hard to say how much I would guess that the 4770 is along the lines of a 5670 which should have been fine on your old cpu so I guess next you might find yourself buying a new gpu to go with the i32100 which is a nice budget gaming chip..

overall for the money on a new motherboard and chip you would have been much better served by getting something along the lines of an am3 board with a phenom II 955 imo, you will be limited in games that require a healthy quad such as BFBC2...

toms uses the phenom II 925 in there latest budget build, you should check it out and be willing to do some overclocking which imo is easy

That would depend on your resolution to some extent but i wouldnt expect anthing to much from a simple CPU upgrade like that.

Mactronix  

An E5700 is already a pretty good match for a 4770. I assume you will see a bit of an increase, but honestly you would have been better off just overclocking the E5700 and spending that money on a newer GPU and CPU cooler.

Yes I know, I used the E5700 in another Pc which cpu and motherboard were damaged (a storm fried my pc, modem, even the speakers....).
So I decided to update my rig...

I read the Tomshardare "Best Cpu for the money " guide, so I decided to go for the i3 2100... Although I´m concerned about it only having 2 cores.... (I´ve another post talking about this...)

^yeah like I said above for around a 120 you would have been better served by a phenom II x4 imo