Depends what you are wanting to improve in terms of performance - the most noticeable all around difference maker in my opinion would be a SSD for the OS disk. In general, everything becomes fairly instantaneous - boot time, application load times, file access times, damn near everything.
I personally would skip a proc upgrade for the moment, especially the FX 6300 - those APUs aren't that amazing unless you are accustomed to playing games without a separate graphics card. If you want extra muscle, I would go with a 1090/1100T or a bulldozer/piledriver proc. I have an 8150 in my rig and my buddy has a 1090T in his, both of them take care of business. They're coming down in price thanks to the 8350s being released but it's a little overkill unless you do a lot of processor hungry tasks like encoding.
I personally prefer Nvidia GPUs - stepping up to the 600 series would be a bump to your FPS, especially if you could afford to go at least to a budget 660/660ti.
Let us know what games you play or what you're wanting to improve performance for and I'll see if I can narrow down your options.
I play just about everything from BF3 to Crysis 3, to League of legends and Minecraft...
and also, i dont think i could afford to get a 660 because there higher in price.. i dont usually get money very often, it would probably take me several months just to save the extra 50 or so.... and not to mention out of a job atm.
but how much of a upgrade would getting a SSD be? and what brand should i get?
if you play BF3/Crysis3 then I would go with a GPU upgrade. Those are both GPU hogs, the 7850 wouldn't be half bad.
If you do want to go with an SSD, I personally like the Samsung 830/840 Pros - very fast, very reliable. 64 is big enough to fit the OS, but I would go with a 120/128 so that you can have all your program files on there as well.