C5's are a classic and are near state of the art regardless of price. That is why you rarely see them for sale, I own a pair purchased in 2002, one of the last pair made, the C2, C4, were already on the market.
The speaker reproduces music, the bottom end goes low enough for 90% of the music recorded, and if there truly is bottom end of a recording, you will feel it.
The bass is not boomy, fat or forward, it is defined, tight and quick, now to some that may make it sound weak, but that is not the case.
That mid-range is out of this world, so coherent; in fact, the whole speaker is coherent. The speaker just sounds right. Elegant in design and fits into any room décor.
Only speaker I might replace my with would be the new Sapphire. I never thought the C2, or C4 were better then my 5s or worth the cost, the Sapphire I might have in the market again, perhaps for the last time.
I wish you luck finding a pair of C5's, to me they be worth any asking price, they are a bargain when compared to speakers today that cost double the price of my C5's.