I think these are the best speakers I've owned to date. I don't know what the factory xo's sound like but these Z19's are wonderful. I have to sell a couple of pairs to appease the wife but I think these are keepers.
One thing I've noticed is they need very little power to make a lot of sound. I am hooking them up to my AU-D1 II tonight. In the future I can see a tube amp but since I know little to nothing about tubes this will take some research.