Tue Aug 23, 2016 4:45 pm by bob
I stayed away from answering this because of my lack of recent experience on AMD CPU's and running lots of WoW sessions, but I agree with what MiRai has said.
That said, I did research a little when the question first popped, and to my eyes and what I've found on google, the AMD CPU's proposed are of lesser performance than an i7 4770, so might get a little tight on 10 instances.
The GPU I'm less certain, but it looks to be an upgrade. I think that a 970 would be the better bet (more vram), although 10 WoW's might be tight, but this depends on settings of the game. I've just read on dual-boxing.com, that a guy is running 20 instances on SLI 970's with approx. 30% GPU usage on each. No idea what game settings or resolution he is running though.
Ram will be very tight. These days, you almost need to ensure you have 2GB per instance.
Overall, my thoughts are you would be hard pressed to get what you are after with upgrading only 1 of the items, and would be more likely to need all 3. This is assuming you are planning on the forthcoming legion.