The best six seater?
Kingair B200, with a full Raisbeck Conversion. Then if you dont want to fly VIP's/Exec's stick another 7 seats in and drive it like a Toyota Hiace. Or take the seats out and drive it like a one ton Toyota Hilux lwb.
Remember there is only one thing better than Pratt and Whitney, and thats two of them. Its only aircraft owners that do not fly themselves, that like to buy erries with one of those.