If i have 6,000USD then i will buy RIG set, i will do ETH mining. Eth is currently one of the most profitable altcoins. So some of the best VGAs I'll buy and I think I'll be able to get the best hastrates with that kind of money. But all the decisions are on you because you know what to do.
Thank you very much for your help! What kind of RIG set you think I could manage to build? Any clue about MH/s GH/s? Haven't done much research on ETH (about diffculty increase), how long a RIG setup could still be profitable (considering the diffculty levels)?