I'm no audiophile, so my observations are not nearly as informed as many here. BUT, I find them amazing. I came from 3 Ascendacoustics Sierra-1's, also from an excellent internet direct company (Dave Fabricant), and a very fine product in their price range (and above). However even I can tell the Cat 8C's are another animal: a fuller, richer sound, yet so detailed, and never fatiguing even when I rev everything up to 0 (fortunately neighbors' houses are not too close!) I know this is not a precise analysis, but probably the best I can do.
I also note that they go great with the SubM/HP, x-overed at 80 Hz. (And I have 5 Ascendacoustics HTM-200's as surrounds.) And since the Cat's are self-powered, my Onk 3008 AVR is only driving the surrounds, so there's enormous headroom available.