Xanthippe is said "Ksan-thee-pay" in Ancient Greek, and
Xena is a made-up name, maybe based on the Greek
Xenia, which is "
Ksenia" - it's only modern English that turns the X into a X sound. So maybe both
Polyxena pronunciations are right, it just depeneds if you want to say it like they did back in
Aristotle's day or if you want to modernize it.