I also have a machine grey CX-9 and I would say yes to wax application! At least once a year depending on your conditions. I don't think six months is too early, but I would do a clay bar treatment before polishing/waxing, if you haven't already. I have also heard good things about Collinite 845, but I don't have any experience with it. I have used Blackfire One Step (liquid polish/wax) and P&S Beadmaker (spray-on sealant). Both products are good, but the Beadmaker is a great last step product. It leaves a very, very smooth feeling surface and looks excellent.
Chemical guys butter wax makes darker paints look amazing but it really only keeps the look for a few weeks. Griots best of show wax has the same results for me. Longer lasting but not as much of that wet look, I like to use griots 3in1 ceramic wax. Looks great and protects for quite a while.
Future reference, typically once your paint is on for 30 days, its cured enough for waxes. You shouldn't have to use a compound or polish with new paint unless there's a scuff or light scratch and if you do, make sure you use a fine cutting compound.
I should note, my recommendation for clay bar treatment depends on the condition of your paint. When my car was delivered to the dealership it had less than 20 kms on it, but when I ran my fingers over some areas of the paint, it felt a bit gritty/rough to the touch, likely due to iron fallout exposure during transport to the dealer. Mostly on the front fenders and the lower part of the rear doors. If your car's paint doesn't feel like this, then you can skip straight to the last step product.