Mains Power Cable DIY

Do yourself a favor and don't overthink it.  Purchase bulk ac cable, ac power plugs, and iec plugs from reputable manufacturers like Furutech, Neotech, or DH Labs and then carefully construct the cables by attaching the plugs/iecs and connecting the wires and shielding.  Some like PCs with shielding for front end/digital components but not for power amps.  IME, shielding is never a bad thing and most of the already constructed power cables available are shielded.  I have had good luck with both Furutech and Neotech bulk ac cables but if you check the links you will see a couple of the Neotech offerings use UP-OCC copper, which is no longer made.

Regarding your "panel to stereo" circuit, at a minimum, dedicate that circuit for use only by the stereo.  Beyond that it comes down to personal preferences and how far you want to go.  I have separate dedicated circuits for digital, front end preamplifiers, and a third totally separate circuit for my power amps.  Each circuit is 20A and uses oversized 10awg wire.  I am sure having three circuits is overkill.  Some will probably tell you a single circuit sounds best.  If you are using a distribution box for your whole system, then you don't need more than a single circuit.  Some add whole house surge protectors, power regenerators, and other stuff.  Good luck.

Great and thanks for the links

I like Furutech cables. For the amp I would do DPS-4.1 with FI-50 NCF plugs. Or FP-S55N with the same plugs.
As fat as dedicated line, I had the electrician run two dedicated lines for my system, 12 gauge romex double run on each line so that I can have two duplexes on each circuit. This provides flexibility to either run an amplifier on it’s own circuit and run your sources on another, or split digital and analog.
I use Furutech GTX-D NCF Rhodium outlets. And I sold my Puritan PSM156 power conditioner as I just prefer everything connected direct to wall after the dedicated lines were run, using good power cords and outlets. 
YMMV