Thanks for your valuable opinions!
Well, I'm considering buying a new PC (which I mainly use for a job), so that's gonna be i7-3820 with a) cheap cooling and GTX 580 or B) nice watercooling and GTX 560i.
Honestly, I feel I'd go with 560Ti, just because I do not play anything else but flighsim once a month, and paying about eur200 more for almost 0 FPS and slightly higher AA settings is not for me