Yeah, it's a crazy hobby, and diminishing returns are always at play. You pay a lot for that last little bit. I could never defend it rationally, but when you hear something you like better it's hard to go back. For me, the Conciertos are worth it (at least at used prices).
It all depends on your budget, and how much you value incremental improvements. Women spend money on jewelry, and I'm sure most of them couldn't distinguish between a real diamond and a fake. but to those who can....
I hear meaningful enough differences in cables (even digitals) to keep trying different ones. Some people don't. You have to figure out if you're one of them and what it's worth to you.
And as I said about the Xindaks, other cables are better, but the FS2s get you a significant amount of the way there at a resonable price. If you buy your cables used, they're mostly broken-in already, and you'll save a lot--and you can resell if you don't like them. Once you're settled on the components you want, you can fine-tune with cables. Some would say you'd get a lot more by trying different speakers, and I agree--I'd love to try dozens of different speakers in my room, but the logistics are prohibitive.
No cable works for everyone, or every system. I lent my Xindaks to a friend, and he preferred his Acoustic Zens in his ribbon system (less extended but smoother on top).
Good luck with your search.
