It won't be twice as fast as a 290x on 28nm. My guess is it will be around the 980, otherwise there would be no reason to push 300w. This will be an expensive chip for them to make. Hopefully it's a lot faster than the 980, otherwise NVIDIA will just release "Big Maxwell" as Titan II for $1000. I just don't see AMD getting a lot more from their architecture on 28nm.