Dedicated 20 amp lines/should i use a sub panel

A balanced power transformer is most definitely an improvement and well worth it - I use them - one for my power amps and one for the front end.

The slight hiss you hear is generated by current running through resistors,  transistors and other components in your amplifiers - all electronic components have this to some degree.  Some resistors have lower noise than others, same goes for Transistors etc.  Its not something to worry about.

Good Listening

Peter

@Al- Yes, it makes sense to measure the voltage to narrow down the issue. I haven't upgraded the Parasound Halo-A21 amplifier because of two issues, room acoustics and power quality inconsistency issue that we are currently discussing. I have somewhat handled the room issue with GIK hybrid Alpha panels and wanted to ensure a good clean power feeding my music room before spending any money on the electronics. I have more or less decided to go with Pass Labs XA100.8 mono blocks when I am able to resolve these issues. 

@Peter- Is it worth spending $10K to get a branded transformer from Equitech or Torus instead of getting a Commercial Power isolation transformer at a much cheaper price?

Thank you all for responding to my queries.

So many responses, I apologize if this was already said:  make sure all lines come off the same side of your 220 line.