All passive and active circuits add distortion (whether they measure different or not). All passive xover parts add distortion (some of which can be measured). All brands of resistors, wires, capacitors, coiils and their implentation all change the sound. The ear can hear what is lower distortion. Those that listen to parts and execution absolutely know this. Most manufactures know this. This is why you see more expensive parts being used.....it is not just to "sell" you something....it is mostly because they have spent hours and hours trying to find the lowest distortion sounding parts to make the sound the best.
Active xovers also distort the sound. Everything distorts the sound. The less stuff you have in the signal path.....the better. Sinlgle driver systems with augmented super tweeter and woofers are the real deal. When you hear a great sounding amp drving a great driver with no xover whatsoever......OH MY!
However a simple two pole line level passive xover right before an amp can blow your mind, as well. So, if you bi-amp that way.....the results are super. Then you can add a transistor amp with its own processor to do bass extension. Many ways up the low distortion ladder.
Happy Thanksgiving! We are all so blessed. Pease share with everyone.