120v vs 240v


Doing a electric panel upgrade and thinking of running 3 new dedicated 8 gauge circuits, 2 for possible future 240 v  ( which can also be 120v) monoblocks and a dedicated 20 amp for other gear
What are the pros and cons of 240v  vs 120 v for amplifiers

also how many isolated ground circuits do I need?

 Thanks 
digitaljoseph
DJONES he wants to know if runing the amp on 230v will sound better yes it will i my amps and preamp run on 230v i went down that road no power cord will do that
Clarification 
perhaps my prior post was a bit inartfully stated

i am trying to accommodate future potential needs while addressing present and future costs.  I have no issues changing out breakers and plugs in the future to accommodate a potential 240 v amp., as last ng as the wiring and ground are adequate Definitely doing a new panel as I am adding 2 Tesla supercharger circuits, summer kitchen etc
Post removed 
i get it go on amazon type in leviton 5842-i  plug i went down this road if you do run #3-10 awg from pannel to plug now you can run any thing from 100v to 250v consult a electrician tell what you want