Thanks for the update! I thought you would find a lower crossover point works better.
I think lower than 60 Hz will be too low, but that is based on my experience with large PA systems, not ones in homes.
Keep up the good work and let us know what you find to be the best.
I don't know how accurate you can be with the frequency, but I like to set things at frequencies that relate to musical pitch, i.e A= 440Hz.
At 60 Hz, you are close to B1 which is 61.74 Hz. Try C2 = 65.41 or 55 Hz = A
https://pages.mtu.edu/~suits/notefreqs.html
If you crossover lower than that, you are letting your mains handle a lot of low end and use amp power for them, and only using the subs for one octave of bass if they will go down to 27.5 Hz flat. Below that, pitch is not very musical and mostly used for effects in movies unless you listen to pipe organ recordings that can reach C0 = 16.35 Hz.
As a recording engineer, I was mostly concerned with acoustic and electric bass, kick drum etc where low E is 41.2 Hz. Piano goes down to A0=27.5, but not a lot of music is written for those notes.
On AVS forums, home theater guys worry about getting flat response down to 15 Hz LOL. How low can you go!