Someone from Planetside will say something here shortly probably ,
but if you ask me until they implement multhreading in the preview 
or-and some GPU accelerating(do not count on it) etc. 
you would be better to use a small render with low settings (the quick render camera node for example 

 ) 
especially with the power you have under your fingers it would be much accurate and faster too. 
I certainly would use it if i had a computer like yours. 
In fact i use crop renders with low setting more and more instead of the preview . 
It is more accurate this way. 
Sometimes i think instead of the preview window we have now 
maybe Planetside should put the low render camera window direct there and should do the rendering automatic anyway