The best gpu for scrypt mining is the Asus strix r7 370 4gb. This bad boy is power efficient. It draws 110w and gives you 15mh (17mh OC) of ethereum mining. Right now you can get them with a $30rebate brand new. https://www.amazon.com/Radeon-Overclocked-256-bit-DisplayPort-Graphics/dp/B00ZQ3QVJK/ref=as_li_ss_tl?ie=UTF8&qid=1471500653&sr=8-1&keywords=asus+strix+4gb&linkCode=ll1&tag=technology304304-20&linkId=15ea6672c1c998b748dfe71d0d8ab041


 I have 5 of these gpu´s in my rig. To power my rig I chose Evga 1000w Gold with 6 pcie vga cables.

Very important to get a real good power supply.