Sheesh. I didn't see this guy ask:
1. Is Xzilon any good?
2. Was I ripped off when I payed for Xzilon?
3. Should I remove Xzilon and replace it?
But, everyone thought to chime in and trash it. I'm not sure why. Maybe it's overpriced, but he just wanted to know what to top it with. However, it's probably no better / no worse than any other sealant.
So, to answer the OP's question, it seems Xzilon is closest to or is a polymer sealant - as is NXT. So, your best bet would to not use NXT, as it wouldn't make much sense to layer 2 different sealants, but to top it with a carnauba wax like Xzilon seems to recommend.
You would probably be best off with a non hybrid wax like P21S, a Bouncers or Dodo variant, or maybe even Souverän.