Sorry for my late response. It is normal to have problems with my post because it is a bit outdated. I'm not active miner because of the high electricity bills in my country and the lack of space in my apartment because I am poor student :D Your rig is excellent for education purpose and you cannot expect to make a big profit from it. You also can calculate your income using this. Have in mind that not only kh/s is important. If your video card is power hungry, your bills will be higher than the amount you had mined. Search for the cheapest mining hardware with efficient hash rate/power and you will find nice threads, which can give you ideas for next purchases. If you have any questions, feel free to ask me :)