I was having an issue with the sound being a bit muted on the highs. Couldn't figure out how to fix it until I changed the woofer low pass to 18KHZ. That is high, but the woofers are rated for it. The result is that it really filled out the sound. Here is how my freqs are set.
I know most people say to low pass the woofers at 2500 with a low pass overlapping the sub, but for some reason it just sounds better with it at 18KHZ and tweeters high passed at 2500.
With these settings and the gains where I have them there is no distortion that I can perceive.