If I install '20A dedicated circuit'

Power conditioning stuff still helps. In my experience, anyway. That doesn't mean you should reconsider the dedicated line, though

Like most things "it depends!" Primarily on the quality of the AC supplied by your power company. Dedicated circuits cannot eliminate voltage fluctuations (not good for tube gear especially, because the bias current is affected), nor can they (without additional hardware at the panel) provide surge protection.

And if for some reason you wish to use balanced power for your front end stuff, you'll still need a balanced power unit.

Start by checking the wall voltage at different times of the day and night on weekdays and weekends. You can use a simple volt/ohm meter and record the readings. That should tell you. You certainly don't want the voltage to vary more than say, from 119 to 122 volts.

Once you

As others have said, it depends. In my weekend system, I have two dedicated 20A lines but they still vary in voltage more than I like. I use an AVR and filter.

Kal