Is this a good Cpu upgrade? or should just get a gpu

I currently have a PC with
AMD Phenom 8650,3 core processor
4gb ram
Nvidia Geforce 9300gs

Will getting a Phenom 4X 940 (AM2+)
be an effective upgrade for 60$?
I mostly play minecraft at 40~65 fps,and record at 20~25fps,how much more fps will I get?

Or should I get an Radeon HD 6770
Which should get me more FPS(PS: gonna get a new computer on January, CPU Only for part time use)

-Thanks