http://www.tomshardware.com/reviews/sapphire-vapor-x-r9-290x-8gb,3977-5.html
I know it is total system power consumption, but there is little difference between the gtx 970 and the r9 290x 4gb on the review, while the actual tdp of the 970 is 145W and the 290x have 300W, which is a huge 155W...