Teflon is very tough and very heat resistant, so the teflon jacket is generally much thinner than a PVC jacket or whatever. 14ga is perfectly respectable for speaker cable, even though your new silver stock seems really skinny. You might want to go with 10ga or 12ga, but 14 is still good. I'm using canare speaker starquad (4S8) right now on my home office stereo, which is a combined 13ga wire. Their 4S11 which seemed way too huge, esp in my office, is a combined 11ga.
I think most mic cable is 21ga, 24ga, or 26-28ga. 14ga is really pretty large. Regardless, I wouldn't use that for your mic cables since mic cables deal with very small voltage levels and are thus much more prone to EMI or RFI noise. If you were to attempt it, you'd need to twist the wires together by hand and then find some kind of copper or tinned copper metal braiding and insert the twisted wires into the braiding, being certain to tie the braiding to ground in your completed cables. I think once you got the wires you have twisted, inserted into the braiding for EMI/RFI sheilding, and then got the whole thing inserted into some techflex, you'd have some pretty bulky mic cables. Not to mention it would be a total PITA.