I agree with DK. Abrasives are not meant to get the paint smooth. Their purpose is to remove swirl marks scratches and other imperfections. Everytime you use an abrasive you remove some of your clearcoat, so it is best not to use them unless you have to. You can simply use a clay bar to make your paint smooth if that is what you are after. Pinnacle Paintwork Cleansing Lotion also works good for this. The cleaners in the AIO will also help to smooth out the paint. Don't underestimate the cleaning power of AIO, it works better than you think.
I don't think I would recommend the 3M Perfect-It Show Car wax over Klasse. I have tried the wax before, it does give a good shine at first, but the durability is not very good. It lasted about a week on my dark color Explorer. Since you are going to invest the time and $$$ into the finish of your car, its better to get a wax with better durability. Here are the waxes that I use over my cars with Klasse
1. Blitz (Good all around wax, great durability)
2. Pinnacle Paste Glaz (For light color cars, not great durability, but O.K.)
3. Pinnacle Souveran. (For dark cars, more durable than Paste Glaz.)
Overall I would go with the Blitz. For the shine and durability that is gives it is a great value. You may not even want to put a wax topper on your Klasse. You really have to wait and see what the Klasse looks like before you decide if you want the wax on top of it. The whole key with a wax topper is not to apply it until you are 100% happy with the way the Klasse looks. If you think you might want to apply another layer of SG in a few weeks after you are done, then don't apply the topper. That way you don't waste your wax, and you dont have to strip the wax off before applying more SG.