15 amp circuit VS. 20 amp Circuit

That’s a lot of gear. Honestly if you weren’t going to run them at maximum output all the time you are probably fine so long as you don’t try to turn them all on at once.

The better your wiring to your stereo, the more likely you are to dim the house lights. :) What you should be concerned with is more current on 1 circuit = more voltage drop, and of course, eventually tripping a breaker.

I’d consider running a 60 A sub panel to your room, and from that panel run 2 or 4 dedicated 20 amp circuits. The big advantage is the 6 gauge wiring will result in lower voltage drop overall. Worth considering an in-panel surge protector as well for your gear, both in the main and in the subpanel. It’s not as good as a series mode device (Furman or ZeroSurge) but better than not having them.

The electrical engineer went to school and studied electric. I would follow his recommendation. I’m a builder and I recommend the same. 3 dedicated outlets. Pretty cut and dry. 

Maybe more of a setup Fritz had with his stack of Krell's

@mickeyb  thanks!  Yes I have some one installing 4 dedicated 20 amp circuits . 

First, a dedicated circuit is always preferable. 

Second, no, your loads are absolutely not connected in series. Loads are connected across the hot and neutral, in parallel.

Third, yeah, probably 3 dedicated circuits, all pulled from the same leg (same side of the breaker box) to minimize potential ground loops and different ground impedances.