Is it CPU or gfx card limited? Does more cores help, or just outright speed.
Combination of both!
Obviously like any game, it will grind too a snails pace, if the resolution is high enough an the GFX card isn't fit!
Sadly, KSP will never likely support multiply monitors, due too an oversight on the Unity Engine.
But the game is primarily limited by your imagination an cpu power!
KSP is compiled on the latest version on Unity version 3.5!
This means the game has better memory management + MultiThreaded (NOT Multicore Yet)
So Game engine, Phyics Engine, Rendering Engine, Sound, Input are spread out over the Mutliple Threads an usually 2 Cores.
To give yourself the best gaming experiance, I strongly suggest a modern multiple core CPU. An Most importantly, Overclock it within an inch of its existance, because the extra Mhz help when your craft is made from hundreds of parts!
My PC 4.4GHz i5 2500K, will happily handle 500+ Parts, but its still 5-10FPS!
Too summarise, More Mhz, More Parts!
On Topic, I managed a GyeoSync orbit! Thanks!