@holmz , no argument from me. I would just like to state for the record that slow phase shifts are likely to be less noticeable than abrupt ones. It is really what happens at the cut off frequency that counts. I avoid your scenario almost entirely by using one way main speakers. All I have to worry about is the subwoofer crossover and one phase shift. IMHO the best crossover is no crossover. This is not an endorsement of dynamic "full range" drivers. The crossover is the lesser of two evils and those drivers are really not full range. Most of them have a 6 dB/oct mechanical crossover to a whizzer cone. The only real full range driver I am aware of is an ESL and even they have to have some wizardry performed with their transformers to make it work.
@fleschler , sounds very nice. I like cherry very much. Echos are very disruptive.