A lot of games will show a very marginal improvement when you go from an e8400 to a 2500K , and you definitely dont need a 2500K to run games at that resolution .
IMO your smartest upgrade is to buy
1/ a bigger 1080p monitor
2/ the graphics card
Thats the plan. But I want the main stuff. Will get a better monitor later. And I am NOT upgrading the video card. Not till the next generation comes out. My 5850 is almost as good as the 6950. Its just a few FPS below. So any upgrade would be almost parallel in regards to the video card. But since a lot of games are recommending a quad core. I think its time to go that route!!! I qill upgrade the monitor as well in a few months.
I think a CPU upgrade would be awesome.
Changed my old E8500 for a 2600k.. My pc is blowing my mind (HUGE difference, in loading windows, starting applications in windows boot).
Today is faster to iniciate my windows with steam, origin, asus ai suite 2, bluetooth, marvell lan, msi afterburner, virtu graphics, antivirus in autostart, than my old system only with antivirus and msi afterburner