Upload & Sell: Off
I would say it depends on what you enjoy shooting the most. If you're going to dabble a lot with low light or landscapes, then the iso performance and dynamic range will be worth the shortcomings. If you don't care for all of those pixels or the gains in image quality and want just a solid workhorse machine, then the D700 would be your ticket.
I'm not sure what kind of collection you're coming from now, but it sounds like you have a pretty well established kit with that 85 1.4. Of course investing in lenses rather than bodies is a good preposition and is generally the way to go, but in this case the difference is (rather) marginal.
Personally, I love the extra newer-generation features that the D600 entails, and would go with the battery grip to try to remedy the situation there. You're still not going to get the same control scheme, but it should at least help your hands a bit.