Well, to be thorough, I'd do the DAWN wash after Meguiar's #9 2.0. In theory, the Klasse AIO should remove anything already on the surface, but, I feel that you don't use enough of the Klasse per panel to completely remove every trace of the oils left by the swirl remover. It's just much easier to do a wash and know that every panel was thoroughly cleaned before you proceed with the sealant. If you want to cut corners, yes, you probably could skip the DAWN wash and just use AIO. But, I'd have to use a LOT of AIO for a good peace of mind. So, this means you're wasting more (expensive) product than you need to. DAWN is cheap, effective, and quick by comparison, which is why I'd go ahead and use it first just for good measure.
If you use any other wax, like GC, use DAWN before applying any sealant...
:wavey