I'ts probably going to take you a while to get a 290 at their current price if you're paying with your current mining proceeds, not to mention you may well be burning more electricity than you are mining at that kh. It will help tremendously if you did get the upgrade though. My 290's generate about 875 kh each. You will NOT be able to game with them when you're mining however, unless you drop the intensity down a lot (sacrificing kh) and play little flash games. Pretty much consider it all or none, I've cut my gaming down tremendously since I started mining, games just don't compare to incoming extra cash for me.