>>There was a HUGE dip around my crossover point

That is nature's way of saying "fliiip the phaaaaaase switchhhh....". If your sub and mains are out of phase they will cancel at the crossover point and you will get a big dip.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8