Free elecricity? get an hd 7990 or an R9 390x2, they're gonna cost you but they're very very good. If they're not in your budget then look for R9 390(without the x2) or an R9 290, these can be bought cheaper than the rx 470 and do as well or even better, they're power mongers though
I am somewhat on a budget and YES free electricity where i stay so i don't care of it's a power monger.
Thanks for your advise, i will see what i can find (used) for a decent price !