The best solution is to have electrician wire you 240 in your house and you will use best of the best.
I doubt a credible licensed electrician will install a 240V branch circuit and 250V outlet to feed a 230V preamp.
2020 NEC 210.6 (A)
(A) Occupancy LimitationIn dwelling units and guest rooms or guest suites of hotels, motels, and similar occupancies, the voltage shall not exceed 120 volts, nominal, between conductors that supply the terminals of the following:
- Luminaires
- Cord-and-plug-connected loads 1440 volt-amperes, nominal, or less or less than 1/4 hp 60 hz
.
60 hz is better than 50
Cheaper to build 60Hz transformers than 50 Hz. 50Hz transformers will work fine on 60HZ mains power. No so for 60Hz transformers on 50Hz mains power.
240V is better than 120.
Watts are watts.
Formula for Power, PIE. I x E = P
P = power, watts, Va.
I = Amps
E= Voltage
Wire size can be smaller for 240V.