I've not read anywhere that someone was complaining that they purchased too much truck. The camper you select today may not be the one you want/need a year from now. I totally support the advice given to first pick the camper, then the truck, just make darn sure you pick the right camper the first time. Good luck with your search, which can be daunting, requires tons of research, but is a lot of fun at the same time.
One thing I did was to read forum signatures here to see what people are using. Most here are very helpful when asked specific questions about their setup, so find the camper you think you want and ask owners what they like/dislike about their rig combo.