Fury uses less power than a 290X that he currently has so it'll put less heat in his room too. http://www.anandtech.com/show/9421/the-amd-radeon-r9-fury-review-feat-sapphire-asus/17The Fury certainly won't address the power draw and heat output issues that 302efi wants to curtail.
Vs a 1070 its about a 14W difference in games. https://www.techpowerup.com/reviews/MSI/GTX_1070_Quick_Silver_OC/27.html
A Fury is significantly faster than either a 290X or a 8GB 390X or 480 in plenty of games. It also does better with DX12 games too. That doesn't sound like a side grade in the least. Realistically if you're not gaming @ 4K you'll probably be OK with 4GB for a fair while yet with most games.It also looks like its days are over and will at best become a side grade with memory limitations.