Main vs. sub panel for dedicated lines

@noromance 
Ok, I get it.

I feel that I did not provide enough info in trying to be succinct in my question. 

In my current house I have 3 dedicated lines serving my system. These lines run from the only panel. I used  2 lines for analog and 1 for digital. 

The new home is a remodel of an previously built building which is serviced by it's own meter and electrical panel providing 200amps service. I have added an addition to this building which will house 2 bedroom and  2 bathrooms, one  a full bath and utility room and and one a 1/2 bath. One bedroom will house the audio system. I was going to use the sub panel for this addition to provide more lines. The original main panel could be used for high current items in the utility room.

I have a experienced electrician who I consult with and helps me. Most interior wiring for both homes I did myself. I will consult with him on all aspects of my plan and adjust accordingly. He is not an audio enthusiast. 

My thinking was I would use 2 10ga. dedicated lines for my system, 1 for analog and 1 for digital.  Both on the same leg of the Panel serviced by 20amp breaker for analog and 15amp for digital. 

My question was to solicit from experienced audio enthusiasts suggestions on which panel I should use to provide the dedicated audio lines. My initial thought were to use the sub panel.

I thank all who have provided input and hope to receive additional thoughts.

Thanks, Mike

How far away from the main panel is the listening room and the two bedrooms and bathroom? The only reasons for a subpanel is to limit the voltage drop over long distances, or to group together outlets in a common area so as not to overstuff the main panel (i.e. a garage woodworking shop with numerous 240V circuits for power tool motors).

To give you a perspective: a #12 branch line carrying a load of 10 amps can be run up to 75 feet to keep the voltage drop under 2.5%. That is a lot of amps. If you go with #10 wires, then you can go up to 125 feet for a 2.5% voltage drop.

Since you have a dedicated service drop for the second structure, I see no reason for a subpanel with only three audio lines, one GFI bathroom circuit and one or two AFI bedroom circuits. Unless it is quite a big house.

Mike, if you're using 10 gauge wire the breakers should be 20A. There's no reason to use one 15 and one 20A. 
If you use 10/2 Romex, you would use two 20A receptacles for your audio.

As stated before, use a subpanel for audio. Main 200A panel will have high-current draw appliances, lighting, and household devices.
Each panel will have an 8' ground rod, check with electrician for code.