kb6kgx what are your client's needs?
No clients? Then what are your perceived needs/wants?
I currently use (or have used all those Nikon bodies.)
The most unacceptable was the D610 which had the worst AF of the bunch... I sold it after it's terrible showing for shooting league soccer... It simply couldn't track the action (however my current D7200 can) and does! btw, the D610 was totally blind in low light scenarios... Also the D600 series cameras feel like toys in the hand... seriously lame user interface.
As for the D500 it has absolutely fabulous AF and I shot with it for a weekend (league soccer). While it tracked the action with much finesse, for me it was a major disappointment in IQ (dynamic range wasn't close to my D7200). After lengthy testing in my studio I decided to return it. Please check DxOmark, they rate if below even your D7100. That said wildlife shooters and sport shooter love it..
However the lion's share of my client revenue stream is with portraiture, fashion (editorials and catalog) and lifestyle location and events. I simply needed more dynamic range than the D500 brings to the table. Although I loved the ergonomics of it's Pro User interface. Tough call here, listen to what others have to say about it, I'm an exception here since I primarily shoot in a studio.
As for the D700? I love both of mine, I now have two... Look an MPB for (like new) and you be a happy camper.
The D700 has a Pro interface, love it's ergonomics... great for location work HUGE dynamic range. And yes it's a mini-D3. That said, the D3 is superior several ways, it's AF sensors are a tad more responsive than those in the D700... And it's build quality is second to none.
In my humble opinion, the D700 is by far the best "Value/worth" in today's marketplace.
You'll pay at least twice if not three times as much for a D500... Again a difficult call (unless you're tight for cash)
However if you are serious about shooting studio assignments the D3x walks away from all those cameras. It is my workhorse and has paid for itself many times over. Been shooting with it for a decade and it's equal to my D810 in the studio.
Yes my other camera is the D810. It's fabulous when I need the resolution, albeit those large files are a liability so I only use it if a client wants the High Res it yields.
Bottom Line? Keep the D7200 it will give you ample resolution and it's the best sensor Nikon has offered in a DX format (again DxOmark and others have confirmed this).
Simple add a D700 to your mix... Nikon made over 540,000 D700's, they are everywhere on the used market now.
I just purchase one (less that 6,000 clicks) that came in the box with everything it shipped with a new on for $424 at mpb
For those who say the D700 does not have enough resolution? Really? Please download and check out the image below shot with a D3 (same resolution). Besides love the way it renders colors... Nikon did something special with that sensor.