AMD R7 and R9 are overpriced for what they provide because of all this cyrpto currency who ha.
Nvidia is probbaly going to be releasing their 800 Series Maxwell very soon, since we just got the Black TITAN and 750 Cards.
If this was just a architecture refresh, id say go ahead, but since Maxwell is a new Architecture, Id wait for the release of the new series.
Maybe we'll get some AMD Price Drops, and with Nvidia, you'll have a new architecture that wont be out of date in a few weeks/months. xD
My personal Opinion