100v,115v versus 230v

True your power amp probably runs on 400v rails

Only if it’s a tube amp! Solid state amps usually run +- 100 V or significantly less. As I recall, a 100W (@ 8 Ohms) amp usually has around +- 50 V.

Yeah, nothing I'd like more than to run 230V in this apartment... :)

Sadly almost all American outlets are 110V, with rare exceptions for large appliances.  Still, the potential is there! I mean, high voltage = less current, less voltage sag during drops.

Of course, you could also get a Sander's MagTech amp, which does a pretty good job of compensating for this.