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
Consult an electrician to get advice based on the codes in your area. I can't figure out what you're trying to do. Figure out if you want 240v amplifiers or 120v first. 
CLEEDS the the plug that is needed is a leviton 5842-i i have 2 in my home in stall by a electrician 125v 20amps top bottom 250v 20amps my amps run on 230v to run 125v change the power cord thats it 230v powe cord is a nema-6-20p to c13 iec my amps see the voltage from 100v to 250v no change of the amp is needed
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