mypersonally thoughts are, if you are going anywhere near / along power lines, there's no question, go optical.
there are tons of arguements re: sound quality from optical vs, coax, you could have a coax cable made of belden 75ohm cable w/ good connectors for fairly cheap (certainly cheaper than optical will EVER be) but of course being copper-based its' more prone to interference. even if some people feel copper/coax will yield a better sound, i would think that improvement would be far outweighed by data loss / interference.
i did a similar install and am using a 12m audioquest optilink 1 (about a $300 cable in this length) and love it.
there are tons of arguements re: sound quality from optical vs, coax, you could have a coax cable made of belden 75ohm cable w/ good connectors for fairly cheap (certainly cheaper than optical will EVER be) but of course being copper-based its' more prone to interference. even if some people feel copper/coax will yield a better sound, i would think that improvement would be far outweighed by data loss / interference.
i did a similar install and am using a 12m audioquest optilink 1 (about a $300 cable in this length) and love it.