Dedicated line, how many outlets two or four?

I put in 2 circuits so that I can put junk like switching power supplies for TV streamers on the other circuit.  I put six outlets on each circuit.  However, once you have a good poer regenerator, you'll find it is plugged in and most audio components are plugged into it.  Mine has 10 outlets on it and all but 1 is full.  Once you go down the high end power supply rabbit hole you'll need a lot of outlets.

I used 10/3 just as Erik describes above.   This has the added advantage of giving you access to 240V if you have a piece of european gear.

Just one item should be plugged in .. a very large power conditioner/generator. 

I did 5. 

I’d absolutely do two as it won’t cost all that much more to run another line.  Also, you can plug noisy digital components, power supplies, etc. into one outlet and other analog components in the other so they’re completely separated.  FWIW.

I ran one 12 awg wire to one Cardas 4181 wall plug. plugged the Saturn 103C conditioner into the wall, then all of my components into the conditioner.