I can get the 560 a lot cheaper, secondhand I can even get it for 100 USD or so. If that would get me another 2 years, I'd be very happy.For modern games, yeah, but why would you want a 560? There are much better cards in the market. You'd need to OC the CPU though.
And yes, I plan on overclocking the CPU.
That's true, but won't it be made on the same engine as GTA IV? I think the 560 should make it possible for me to play that game.GTA V isn't even announced for PC.
Is the RAM fast enough?4GB is good.
Honestly, I'd sell your PC and build a new one
I don't want to spend a lot on the PC, mainly because my (gaming) future is unclear. Don't know if I'll still game in 3 years from now.