I am guessing this is a gaming computer?
I usually like to see people with 2x 4GBs RAM (CT2KIT51264BA1339 in particular), but if you are on a restrictive budget I could understand sticking with 4 GBs. Also, if you are using a 32 bit copy of Windows you can't use more than 4GBs anyway.
In any event, if it is a gaming computer you don't want 16 GBs, 8 at the most. Any more than that and it only helps you with stuff like audio/video editing.
What maker and model is that PSU? You may need a different one if you end up getting a better video card.
Better processor - Most games only use 2 cores and you already have 3. No games use 6 cores so most of the upgrade would be wasted if you spent money here. Only a couple games can use the 4th extra core and none beyond that. I would stick with what you have here to be honest.
Anyway, I would focus the majority of your efforts on a better video card and possibly another PSU as well, depending on whether the current one can handle the new video card or not.
The 560 isn't a huge step up from the 460. Indeed, nothing from the 500 series is much better than the 400 series equivalent.
I would stick with a new series card from either ATI or Nvidia, either the 7000s from ATI or the 600s from Nvidia.
Here is a really good one I would suggest for you that probably won't need a different PSU.
http://tinyurl.com/86qzfhw
It should give you about 50% better FPS in games.