@vinylcat, best leave the amps plugged into the dedicated line. The current draw by amps is non linear, and is in pulses rather than a continuous draw like from a heater. If a transformer (or any type of inductor as found in many power conditioners) is installed, the 'high' impedance of the transformer can slow the current pulses, creating that loss of dynamics that people report.
Even large transformers like 15kVA over at what's best still does not provide the correct solution either, so the best approach is direct as you can get to the street supply, where the impedance is super low.
After a steady use of over 10 years or so my Equitech 1kva transformer is starting to buzz. At the moment it feeds sources only, the pre-amp and amps are direct into the wall (dedicated circuit coming). As a replacement a Denafrips BIC500 is on its way. Rating is only 500VA, for sources should be just fine. It uses the same principal as the Equitech Voltage-0-Voltage balanced output.
The buzz was explained by Equitech, it's not a matter of mechanical issue, rather the noise from the load harmonics are transferred to the primary. The cure for that is to add an inductance on the primary, another isolation transformer, which is a bit messy, so will try the BIC500 first, see what happens.