I run 25 clients on my I7 4770k @4.2 GHz + GTX 770 2GB + 24GB RAM. I have low detail, with ultra distance on my main char. Sometimes laggy in Big Cities, but not much. Also, I still haven't got my SSD for multiboxing,(15 clients at 1 HDD, 10 at another) i wish SSD will help. I set background fps to "7", at this fps all slaves flying, walking and so on w/o problems and stucks. Main windows set to 40 fps. If i go down to 20 clients, I can set main char to Max settings with Ultra Distance and slaves at low as well.

So, you can setup Macro through isboxer and when you use instant Swap, graphics will change. The best solution ever! + lowering background fps.

P.S. Somebody got 980 TI? How it is for 4K multiboxing (5-7 boxes)?