Dedicated outlets, 10ga, and what else?

i just did the same thing with 2 runs or 10 g bx cable,& 4 porter hubbell's.you are in for a real treat,BUT,it will take around a month to burn in(so hang in there).read the discussion on "only needs 50" & never doubt yourself,eventually you soundstage will expand beyond your wildest dreams,then the sound will tighten up,enjoy

THHN is a type of insulation temperature rated for at least 90 C. BX is a flexible outer jacketed cable with several insulated conductors inside it. My preference would actually be 10 gauge MC which is a metal clad flexible multiconductor cable which already has a full size ground wire in it. BX typically relied on the steel outer jacket with an internal flimsy aluminum drain wire to act as the ground. Thin wall conduit is also permited in commercial buildings and would be an excellent alternative as well.

I think regardless of your selection they will all deliver the same satisfying effect. Alexandierj gives some good advise that I agree with.