Again, it's more involved than just which leg of the panel you place the breakers on. With single phase power, each leg provides 120 volts referenced to ground. There are two of these legs and the start of getting good power to your gear is to keep each leg at the same voltage to balance the entire house power. The idea is for each leg to provide the exact same current to all the loads which results in a perfect zero current on the neutral. If one leg has more draw than the other, the net result will be current in the neutral. This is the start of power problems IMO - ground loops, RFI/EMI noise, arcing noise (popping sounds thru the speakers when a light switch is turned on/off, etc.) and common mode noise being amplified.
Monoblock amps each draw the same current, but a lot more than the source components so they will tend to unbalance and place a current on the neutral if on the same leg. If they are on seperate legs the total power draw is balanced vis-a-vis the neutral but might not have the same potential across the amps, which can cause ground loop hum. I think balanced will yield better results.
If you only have one amplifier then I would opt to put all components on the same leg. This is because all the components will have the same potential across them with respect to ground and there is, in theory, no chance for ground loop hum.
But that's an ideal - you have to factor in all the power drawn in the house and see if the loads are fairly balanced. If they are not, then it matters not how the circuits are wired; any benefits will be countered by noise, etc. Not only that, but things like computers, fluorescent lighting, power supplies, battery chargers, digital clocks add noise to the power by introducing spurious current from harmonics of the 60 hz frequency. Dedicated circuits, while helpful, will not clean the power to your equipment.
In my new house, I have rewired my as-yet-to-be-renovated listening room and house panel to such an extent that I can use line voltage dimmer switches in my listening room with no ill effects. I had to go through the trouble of figuring which loads are simultaneous, which loads draw what current, which are resistive or inductive and wire accordingly. My system, all RCA interconnects and no cheater plugs, is dead quiet - even with your ear to the speaker. I use one dedicated circuit for each of my monoblock amps plugged directly into the wall and one dedicated circuit for the front end plugged into a Z-Stabilizer. Each amp circuit is on a different leg and the third circuit was placed on the leg that balanced with the rest of the house.
Dedictated circuits and which leg they're on is a start. But IMO, there's more to it. I didn't mean to confuse you, but only to give both sides and relate to what I did (that works for me) so you can see if your case is similar. Sorry, a feeder is what you call a length of BX or romex that you run from outlet to breaker.
