I've never tried Souveran over 845, only over 476S (used a spit-shine technique). IMO the slight, temporary, boost in looks probably won't be worth doing, but that's just my take on it. I'd rather just do dark colors with a Collinite paste.
Never tried #16 over any Collinite; if I want #16 on something I use it by itself. The looks of 845 and #16 are mighty similar anyhow IMO, and I was comparing them on adjacent panels (Audi silver).
Eh, guess I'm not help, I just don't layer different LSPs much any more.