Why would Parts-Express give wrong advice when both that company and Dayton loudspeakers are owned by the same people?
I think it is because the staff are not expert and have little training. That is a guess. I doubt you would pay experienced designers to handle phone calls.
From fielding posts from members who have used their techs, results have been as I described above.
Madisound are much better in that regard, as they have a small cadre of very experienced people.
In addition they have a far better selection of drivers and components to select from. Madisound are my principle go to source, although I do use Parts Express for certain items. The bulk of my business goes to Madisound though.