Is Your Computer Ready for Legion?
With Legion, Blizzard have improved the graphics again. You can still play on the previous settings, but there will be three additional, higher settings above what is currently the "Ultra" setting.
I've just had a quick check on the test realm, as these settings will come into effect in the pre-expansion patch, to check them out.
Currently my graphics card is running ultra smoothly and I rarely drop below 50fps even in raids - my current card is a Nvidia Geforce GTX560ti. However, having played with anything above the previous "ultra" setting, the graphics become obvious and laggy, with the framerate dropping significantly even when simply moving about in a low population area.
My current graphics card WILL, I have no doubt, continue to work well within Legion, albeit not on the highest settings, however, for those who are considering upgrading, I've come across two interesting sites.
One is a comparison site of various GPU's, including cost and performance, together with a suggestion of alternatives that offer better value for money:
http://gpu.userbenchmark.com/Compare/Nvidia-GTX-970-vs-Nvidia-GTX-560-Ti/2577vs2180
The other is a post Blizzard Watch made a while back, fairly recently updated, that discusses all the possible bottlenecks that may occur, and suggesting possible upgrades:
http://blizzardwatch.com/2016/05/31/upgrade-pc-legion/
Game-Debate.com has got Legion's specs set up so you can guesstimate how well your system might perform for Legion.
It reckons I'll be fine. 
Ah that's cool :-)
Although it seems to reckon mine is fine for legion too, at Ultra - but having played on the test realm briefly, I know that's not the case. Unless it's referring to the current "ultra" settings, which is no longer the top option, but just above mid-range.
Perhaps having played several years at the top setting, I've been a bit spoilt :p
I'm currently looking to replace my current card with a 970 - just waiting to see if they come down in price a little more in the wake of a newer one having come out recently, and another rival coming out later in the month.