Why you narrowed it more?
Current Nvidia Maxwell generation is not well prepared for the future so you need to look for perfomance/price/wattage consumption ratio. Which means you start on GTX970 here and that seems to be beyond your expressed money range.
However, GTX960 is very effective card but apart from that it's not a very good investement for the future. It lacks the horses, that is hugely depending on what you are planning to play though.
Prices can be well timed because "shortly" (withing two quartals) there should be new lines from both companies.
R9 290X is very powerfull card (and long) but it's power eater. Apart from that it's a good value for a money. However it's old and I wouldn't recommend it for now, before it was (rarely) much better priced or like a part of AMD contest - return Nvidia GTX970 and get AMD R9 290
I woudln't go here and stay with previous choices.