I've done the cat 5 with Teflon plenum, overall sound surprisingly nice... very high capacitance, you would need to be aware of that when using these... As far as silver solid core in Teflon, I'm sure that you are aware that silver can get bright on you in some configurations. For me that's expensive if I ended up not liking them. My cables that I like best are litz... similar to what you've done but true pure litz in cotton...It you can get some light gauge solid core litz, it is a highly detailed full and dynamic cable. Good luck,
Tim
Tim