Sorry, just spotted this. Cpu is i7-2600, not 2600K? Just wondering why the aftermarket cooler, in the first place.

Ah. I see now. The only trouble with you being in Greece, is I don't know where would be the best place for you to buy, or what prices are like there. So, forgive me for talking in sterling. You'll have to check local sources.

Firstly, upgrading mobo, assuming current one is reliable, and performing OK, won't gain you a huge ammount. A bit better connectivity, and perhaps better control over that noisy cooler, but a lot of the "extra stuff" eg overclocking, PCIe 3.0, won't be available to you with a locked Sandybridge. If you were going to get an "unlocked", and/or Ivybridge, then yes. But it's probably not worth doing that. Personally, I think (provided no PROBLEMS with mobo), you may be better to wait until Haswell is out, next year, and upgrade to that. That is likely to give a real performance boost (time to save).

In terms of graphics card, an upgrade to a HD 6870 will give a decent performance boost, for games like Skyrim, if not at the highest settings. In UK, that's around £120, or £140 for good ones. It would be nice if you could stretch to HD 7850, or HD 7870, which are either side of the £200 mark, in UK, and suspect they may be over budget, in Greece, especially if you do want new mobo, as well. They would give a more significant boost.

Haswell is a new range of CPU's. If they prove to be as good, as is hoped, they are likely to be the "way to go" for upgrades. They will, however, need a completely different motherboard. If you change motherboard now, you either won't have the "option" of Haswell for the NEXT upgrade, or have to change mobo AGAIN. It just seems, if you don't HAVE to change mobo NOW, it's a good idea to wait and see if Haswell proves to be as good as hoped.

If your budget, in Greece, will allow for HD 7850 or 7870 (obviously the 70 is better) then either will give you a significant gain, at 1920x1080.