The d610 is better in low light. The 85mm is a great lens on fullframe.
However, you asked a kind of specific question,so the answer I gave doesn't tell the whole story.
The d7200 is the best crop sensor camera I have used and even though I have had fullframe cameras (and don't now) And may get one again I don't feel as if I need the upgrade. If you bought a d7200 with something like a Nkon/Tamron/sigma 17-50 or 17-55mm f2.8 lens I think you would definetly be covered for an awful lot.
The 17-50/55 would be a great standard lens, covering day to day and most of your car needs. The 50mm on a d7200 makes avery nice portrait lens, the 85 is long but makes a very good lens if your at a distance.
As said the d610 is better at high iso, but the d7200 is also very good. Below are some examples from the d7200
Portrait at 90mm f2.8 (similar to 85mm, but the 85 you have would allow even more seperation if needed due aperture)
Who's my team? by
jaomul, on Flickr
Portait with 50mm f1.8 (note this is actually a d7100, but they are practically the same)
Rogue by
jaomul, on Flickr
d7200@ iso 3200 in dark conditions
Oyur 52 week project-week 13-man made machine by
jaomul, on Flickr