>>since my taste are not a reference, how should I tune my system?

Play music or movie your girlfriend likes, turn the sub off, and ask her to set the sub level by turning the volume *up* until it sounds right. That should be good for a couple of dB higher than you would ever get setting it yourself

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