The input impedance of our Synergy 450 is a pure resistive 25 thousand ohms.
The power mosfet output stage has no thermal runaway issues as bipolar outputs do and share loads and need no bias tracking circuits and have very extended bandwidth so they are the superior choice here.
Power doubles into four ohms and even more into two ohms up to the limits of the maximum recommended 6 amp quick blow speaker fuses.
Fusing higher risks blowing speakers instead of fuses.
Just got home from 5500 mile sea voyge visiting Tahiti and 7 other Pacifuc islands. Back to work tomorrow.
Frank