There is an abundance of good advice here on using Avia for sub level and crossover setting.

Remember, a crossover point is not a sharp cutoff line. If you play an 80 Hz tone through a properly tuned 80 Hz crossover, each of the two outputs will receive half of the input energy. Even below 80 Hz, some of the energy will go to your mains, but most of it goes to the sub.

M60/VP150/QS8/M2/EP500 Harman Kardon AVR-7300 Panasonic AE700U/DVD-S97 Sony DVP-CX985V