Technically you could upgrade although I'm not in the AMD side of the market, so I don't know them too well.
Even though it maybe can be upgraded, you shouldn't just upgrade the CPU. Power supplies only last a couple years and usually can't handle new components or are just not strong enough, your RAM is ddr3, i.e. not transferable to a newer motherboard.
If I were you I'd either upgrade the GPU and just run with it, and return it if it doesn't bring the increase you need. If that turns out to be the case, I'd save up for a new pc.