@holmz -
Maxwell's equations weren't wrong, but: there's much more involved*, when we're dealing with retaining a plethora of frequencies/voices (instrumental and vocal), ambient/room information (height, width, depth) and placement of the afore mentioned voices, within that space. (iow: much more sensitive info, than what's contained in DC or AC).
Even those involved in manufacturing PC boards for more the more sensitive RF systems, take into account the variables involved when choosing materials, as signal speed is dependent on their dielectric constants and possible frequencies to be encountered.
We've engaged in this conversation before, so: I suspect your queries to be more argumentative, than inquisitive. Hence: this post is more for those extant, that are genuinely interested in the Physics of what's what with our wires.
If I'm wrong: my apologies!
"But what part of a stereo systems is like a transmission line?"
*http://www.audiosystemsgroup.com/TransLines.pdf