Properly tweaked 5 R9 290's will get you to 4000+khashes.. Mining isn't something you can do cheap and make lots of money.. You have to invest. Start small with a 7950 if you can find one cheap, then go from there.
Yea i know but i am asking for the best options and you gave one
Found a Asus Radeon HD7950-DC2T-3GD5 V2 3GB for 488$. ( apparently this does 730 khash/s)