Installing dedicated 10 gauge lines

Before you do any of this determine if you really need to.  Get a good quality multimeter (Fluke) and set at a suitable scale/resolution to determine if you have any voltage drop while using your equipment.  Your amp will certainly be your highest current draw AND the current draw will go up when you push the amp to high volumes especially if you have inefficient speakers.  There is really not much point in turning it up to volumes that you would never listen, but if you want a good indicator - turn it up.  A good amp with a good power supply and plenty of capacitor storage will handle the transients - that's part of their job.  You don't need to have split second resolution, but if you see the voltage slowly dropping even a couple or few volts then you might be affecting the amps performance and a remedy might make sense. Sometimes a new, high amperage subpanel close by can be a better and easier fix especially if your main panel is a distance away.  If the wire turns out to be too lite at least the electrician won't have far if the sub-panel is near by.      

FWIW, I just had a 60 amp 240 V circuit installed for my Tesla Level 2 charging station which required a run of copper that alone cost $380 for materials and the wiring came to less than $2K.

So you may want to look at electricians that specialize in EV charging.

The absolute most that you need (unless you have something most unusual) is 1 (one) 20 amp circuit.  That requires 12ga with ground from your panel & a 20 amp breaker.  Use a hospital grade outlet.

From that single outlet use a 15 amp or 20 amp multi outlet strip to plug in all of your gear.  Note: The only grounded component should be your preamplifier.  Use cheater plugs for everything else.  Otherwise you will be chasing ground loops to no end.  If you don't have a preamp then you will have to experiment.

One 20A line is certainly an option. And 12g is fine for short runs from the service panel. But to recommend grounding one component and using cheater-plugs all around is irresponsible.

And the theory for using one dedicated line is to prevent ground-loops. With all components tied to the common grounding buss bar there should be equal ground potential (impedance) unless one of the components is not using a proper grounding scheme.

Not sure why people all seem to want a 10 gauge wire. You only need 12. Also If there is no room for a breaker, use a "piggy back" breaker. It is two breakers sandwiched together that only takes up the space of one breaker. Remove an existing breaker and install piggy back breaker. Be sure that piggy back breaker includes the amperage of the breaker removed. They come in 20A/15A, 20A/20A, and 15A/15A.

Seriously, you could consider more efficient speakers (not everybody needs magnaplanars?) or a more efficient amplifier (what about class A/B instead of class Y?), instead of ripping out your walls to try to do all of this.  I mean, if your amplifier has a top-grade power supply and regulator, any minor voltage drop from the wall conduit should be erased by the conditioning circuits in the amplifier.