I'm probably sounding harsh with this post, but there's no necessity to top 845 with anything.
That although I've never used Souveran, or Fuzion, I'm still betting you'd have to have eyeballs like an eagle to tell the difference.
In other words what I'm saying, is don't underestimate the quality of 845 (let alone the longevity), this is a killer product. That if some other esoteric company was able to re-lable it, you'd be paying $60 a bottle for it.
If you have a well maintained vehicle, or one that's just been properly corrected, any of the Collinite line will knock your eyes out.
You will then become a Collinite "Disciple", sold for the rest of your days.
I have, have been for over 20 years. It's a product which basically has no peer.
If anything, that I would maybe top any Collinite product with, it might be a good spray detailer after a wash to remove water spots, nothing more. Mark