Help in matching pre/amp

Although I have owned a HiFi system for a bit, I don’t really understand all the technical parts of the hobby. I have what I feel is a great sounding system, but curious if my components match well on paper.

PreAmp is Aric Audio Motherload XL Input impedance 50 kOhm; output impedance 400 Ohms with a recommendation to keep overall impedance it will be feeding to 10 kOhms. There is also a 5 step output level control which sets the gain of the preamplifier between 3 and 17.

Amp is a SET 45 designed by Radu Tarta with input sensitivity 2.3 Vrms; input impedance 91kOhm. It has 8 and 16 ohm  binding posts. 

A second amplifier I use is Atmasphere Class D monoamps. 

My speakers are Charney Audio with AER BD3 drivers (16 ohm)

Subwoofer are 2 SVS 3000 micro

I use AER outputs on the preamp to the amps (with balanced to single ended IC when using the SET) and the parallel RCA outputs to the subs.

My questions are as follows:

Does this set up seem to be matched?

What would the best setting for the preamp output control gain setting for the SET and also for the AS Class D?

I have the low pass filters on the subs set to 50 with a slope of 24dB. 

Is there a good reference I can read to help me understand all this?

Thoughts? Comments?

Much appreciated