help,crossover settings

[vine]

Good day,I seriously need help with this,so Yesterday I put My bakkie on a meter,and did a 150.5@38hz,this is NOT a spl vehicle,but a very strong music vehicle.anyways,My port is currently tuned to 38hz,and have 2x12" subwoofers,with all the necessary equipment,I also have an external crossover connected up to the Block,so basicly there's 2 crossover settings,the subsonic I understand,its currently set at 29hz(half octave lower from port tune),what's confusing Me is,I have frequency on My amplifier and the crossover,where do I set Them???NB:I like wat I feel and hear with Them around the 40hz mark,is it correct or NOT?,many Thanks in advance