If this was me and rewiring is not an option, I would look into getting a power distribution center such as a PS Audio Premier and plugging into the one 20-A outlet and seeing if all my gear can be accommodated. It is always better, IMO, to limit the number of audio outlets to as few as practical to reduce ground loops and EMI/RFI.
If one power center isn't enough (monoblock amp draw, e.g.) then I would look to get another power center or an A/V grade power strip and plug it into the outlet without computers or motors on the circuit.
The advantage here is that you don't have to worry about phase leg anomalies (etc) because the power generators will scrub the power input.
But if rewiring is not an option due to cost, then my suggestion makes no economic sense because you can rewire for a lot less than the cost of one PS Audio Premier, let alone two.
If one power center isn't enough (monoblock amp draw, e.g.) then I would look to get another power center or an A/V grade power strip and plug it into the outlet without computers or motors on the circuit.
The advantage here is that you don't have to worry about phase leg anomalies (etc) because the power generators will scrub the power input.
But if rewiring is not an option due to cost, then my suggestion makes no economic sense because you can rewire for a lot less than the cost of one PS Audio Premier, let alone two.