A 19MP image is roughly the same, but still smaller, than the 21MP of the D500. Both these DX options are a step down in resolution from your 24MP D7100. Honestly, you appear to have a GAS problem. We all have GAS problems, so that is meant as an observation, not the casting of a stone.

The D850 is Nikon's top FX camera. You should focus on only the best lenses for this body. Get rid of everything else and just focus on this platform, skipping the super zooms. Unless you have a paying job, you don't need a "back-up" camera. That's just a rationalization for not addressing the root GAS issues.

Given the year-end is approaching, have you looked at your images and identified any equipment that went unused this entire calendar year? These are candidates to jettison. The D70 and D7000 won't fetch much, but I'd think these are just gathering dust. There's probably some lenses in the same situation. The D500 is Nikon's top crop body, but you're paying for a professional-grade frames-per-second speed. Are you shooting sports and / or birds in flight and have a quality 400-600mm lens? Do you need to pay a premium for these capabilities and smaller resolution sensor if they are not part of your usage?

Summary: look at what you have and decide what you're looking to accomplish. Is photography the goal or the equipment? Then, do whatever you want.

Again, thanks to all my friends on ugly hedgehog. I pulled the trigger this morning on the D850 and a refurbished (I've never had a problem so far with refurbs) Nikkor 24-120 f/4 at B&H. I sprang for the new credit card in order to save $250 in sales tax although I need another credit card like I need a hole in the head. I will look towards the Nikkor 70-200 next. BTW, I will keep one of the D7100s and put my Tamron 150-600 G2 on it for now. Will give the other D7100 to my daughter who is still using the D80 we gave her at graduation many years ago. The D7000 will go to my granddaughter who has landed a job as her high school yearbook photographer. Also ordered the Darrell Young book on the D850. I've used his books before and I really like them. I really am appreciative of the kind and patient assistance from my hedgehog friends.