This is going to be a 2 part post.
First, the obvious (based on the title) My wife shoots with a D750. I need to upgrade my camera, and I'm torn between the three listed above. The 750 shoots quite well - we've been very impressed. Is it worth the extra money to go with the 800 or the 810? Any Pros/Cons? Words of advice? We solely shoot weddings and engagements.
Second, what would you say is your favorite "money lens"? The one where you can hold your camera up in the air, at a 45 degree angle, and in poor lighting and still somehow get an amazing picture with? I'm partial to primes, but I am in the market for a zoom at the moment.