[Richard]

Something to think about. Every 6x9 I have seen and most car audio speakers 6" and smaller are designed for infinite baffle installation. Meaning no box or a leaky box. ie a door, trunk etc. Putting an IB speaker in a smaller box/enclosure will limit mid bass/bass response. Any air leakage from rear of speaker to front will also cancel mid bass/bass output. Those speakers in the small kick panels are probably dropping out at 300-600hz at best. Adjust sub crossover accordingly. If the sub reaches that high.