At $.95/ft, I guess you won't "go broke" using this inside a speaker enclosure. If you feel that you can actually hear the difference in this sort of application then go ahead and use it. Although I use Teflon insulated wire for wiring tube amps, I probably use it mostly for other reasons than you have in mind. One of those reasons is that I have lots of it that I obtained at very low prices. (cheaper than new PVC hook-up wire!). I use "zip cord" quality wire for speaker wiring....but not everyone does.
don't know that brand.
I prefer thin wire that doesn't overheat the often tiny speaker terminals while soldering them and is flexible enough not to put any sheer forces on those sensible terminals.
AWG 14 would be to much for me and definitely a no go, if being a rigid solid core.