Vettecor- One of the great things about KAIO is that you can use most *anything* over top of it- wax, sealant, etc. Just pick the Last Step Product that you think you'll like and try it.
I'd be more concerned about what you use *before* KAIO as it doesn't do much (if any) mechanical/abrasive correction and *that's* what really makes or breaks a detail.
As for alternatives to KAIO, the Zaino All-in-One is very nice and contains some fairly mild abrasives. I really like AutoGlym Super Resin Polish, which fills/conceals better than KAIO, lasts longer, but doesn't do quite as good a job of chemically cleaning the paint. The SRP does contain some *VERY* mild abrasives, but they're so mild as to be functionally nonabrasive in many/most cases. There's also the Werkstadt Prime and Strong (sp?). I'm not really familiar with these products but I hear they're very similar to Klasse, almost like a "German version" of it. I'd even consider 1Z WaxPolishSoft to be an alternative to KAIO.