A few products come to mind when thinking about sealants being better than the Klasse twins. This is based on products I've used.
- Collinite 845 is a more durable and easier to apply sealant. Here is my comparison of the two from 2014
Head-to-Head cage match - Klasse SG vs. Collinite 845
- Wolfgang SiO2 Paint Sealant is superior to Klasse SG and 845. It lasts as long, maybe longer than 845, looks better, and has amazing coating-like water behavior. Easy of application is amazingly simply/easy. In a class of it's own from that perspective
- Griots One-Step Sealant has abrasives Klassa AIO doesn't have and when paired with a DA it offers a nice bit of correction and improves the shine in ways Klasse AIO simply can't. Durability isn't very good, but I never ran AIO by itself to see how long it would last. I always applied SG over the top of AIO.
Coatings and some of the high durability spray sealants/"coatings"/whatever-you-call-them are in a completely different league when it comes to durability, water behavior, and ease of use. The other day I applied Griots 3 in 1 on my wife's car and was really pleased. If it lives up to it's claims, it's a 6-month (or better) sealant that applied as easy as a quick detail wipe down. I'd take that any day over the Klasse process.
For any of these products there is no need for an under-layer like AIO performed. Polishing the car, even with a mild finishing polish, will remove defects and improve gloss in way AIO cannot due to a lack of abrasives. If you're not interested in polishing any of the products I mentioned would allow you to go straight from a clean car to applying the sealant.