Unless you _want_ to eventually toast your amp (or in rare cases, your entire house) you do not want to use long lengths of 20/22 ga. unsheilded pairs (that have been daisy-chained God knows how many times) for audio power. Nevermind the likely impedance mis-match. You _also_ do not want unbalanced line level signals going over unsheilded wire, lest you love hearing 60 Hz hum, AM/CB/HAM radio, and AC switching 'pops' over your music. And the pot idea may work well for line level, but definitely not on power signals.
Telephone cables work well for telephones/RS-422/etc... For any other uses they are generally garbage.
Just say no to 'recycled' phone lines.