The black mustang above was topped with 845.. it's due for another polish soon and I'll be using Jescar Powerlock then topping with 845 again. Just my personal preference for this car.
G9.. i will say this though, if you have the extra money, get a G8 with 3" pads to go with the g9.. it will be a pain trying to cut and polish the A pillars and the smaller areas around the bumpers with a 5" g9.
If it helps you any, the G9 stalls out on most places that would have an easier time burning through the paint... mainly the curves. The more you prep, the better it will look.. (i.e. your decon step)
G9 with LC orange flat pads, griots compound and polish.. my first time ever using a polishing tool, took 14 hours but I took a lot of breaks and was being *TO* careful.