I want to upgrade from my 270X to something faster, something faster meaning 390X or Fury (no X here).
Nvidia is not an option because I need OpenCL, Cuda will not work.
Thoughts I had: -8GB VRAM are nice to have, but I dont think I will need that in games -Price/Performance, wich is better? -Does it CrossFire with the W8100 in my system or will it stay my "productivity only"-card?
Get the 390x unless you really feel like burning money or you have some application that needs the extra stream processors.
This is a comparison of the Fury vs the 390x the Fury X would fair slightly better but the point remains. While the Fury X will continue to improve with driver updates; currently is just straight up horrid value for money. with a relatively small performance gap and a large gap in price AMD just messed up . . . badly. As a additional point nether of these cards can hold their own at 4k if the Fury could it would win in my book despite its high cost. Also consider that at 1440p and above you do use more then 4gb of Vram in many games.
R9 390 because its just a percentage point off the 390x, and the Fury/Fury X are horrid from a price to performance standpoint and are also virtually impossible to find in stock at anything but an extreme jacked up price.
The UK distribution of the Fury might be better then here in Murica. Although the pricing is something I don't really know about there, it might be more or less competitive then it is here.