Couple thoughts:
First, I think you're on the right track. Having had my own system significantly improved/refined by upgrading my cables, I've reluctantly accepted that cables are too important to be disregarded.
A comment about the idea of "end game cables". There are such things, but usually they are simply the best and most expensive cables a person has tried up to that time that has satisfied their expectations. It means "I've stopped worrying about cables. (Maybe forever. Maybe until I get another itch to scratch.)
For me it was Cardas Neutral Reference. I'd never heard a single pair of cables make such a difference. I eventually ended up with a full loom of them (not including power cords). I was amazed that 20+ year old interconnects would still be (for me) kind of expensive - but not really expensive compared to new or newer cables.
I strongly encourage you to purchase used. And, if at all possible, try before buying.
One more word of advice, since you started this thread, is to not be satisfied with anything that doesn't sound like the big upgrade you're looking for. My cables really brought out the capabilities of my system. And I learned that many times when people are complaining about the way a component sounds there is a big possibility that an inappropriate cable is what they're hearing.
Track down that review of the Cardas Neutral Reference on Positive Feedback. I'm not suggesting that you'll end up with them, but it's a thought provoking, well written piece and reflects my own experience in this journey.