1. If by "coax" you mean a digital link, then I agree that would be more likely to work than a line-level run, but that is a pretty long run either way. You may have to get a repeater or active cable.
2. If you are talking about a speaker-level output ("no amplifier") then I would use standard 12 or 14 AWG in-wall wire, not coax.
As an aside, RCA cables are almost all "coax" but may or may not be the same coax as used by digital links.
p.s. I have run line-level signals 60' - 100' or so in a professional install. Not a big deal with proper shielding and such. If your room is 30' away, you may end up with 60' of cable, and I do not know the route (how close to other noise sources and such) thus my "pretty long run" comment. I had a 20' run in my room for years using fairly cheap cable, kept away from power lines, and no problems.
"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
Last edited by DonH50; 08-25-2014 at 06:46 AM.