GPU and RAM mean little to KSP. (Aside from over all RAM limiting how many mods with assets you can install.)
CPU, specifically single core performance is the limiting factor due to all the physics calculations. Considering that this is the opposite of how 99% of games work, it's not likely to be improved, quite the contrary; newer cpu's are going the way of more and more cores, further diluting single core performance. (Currently KSP can use multiple cores if there are multiple vessels on screen, one per. You can't split a single physics object up between cores though.) Barring some huge advance in multi-threading physics calculations on a single object (no small task mind you), it just is what it is.
Why is "multi core'ing" a single physics object difficult? Well, to use a very simplified example; imagine you have one dish to wash in the sink, with one tap, one dish rag, and I give you one helper. Do you take turns scrubbing? Wasting time passing the dish back and forth? Do we break the dish in half, each wash his piece, then re-assemble them at the end? Do you hold the dish and operate the tap while he scrubs? Do any of these sound faster or neater than just washing the dish by yourself? Now imagine I give you 7 helpers! 8 people in total...how will you utilize them to wash that single dish without having them get in each others way or just complicate the process? Kind of sounds like the fastest, easiest way is still to have 1 person just wash the dish while the other 7 watch right? Now imagine that for every helper I give you, I make you all younger, thus making all of you less proficient at dish washing; who can wash a single dish faster? A lone 40 year old, or 10 4 year old's? (One powerful processor vs. several weaker ones.)