+1. I know you say you're displeased with the d7000 noise performance, but what are you comparing it to? you should at least have some concept of what is reasonable to expect. You can't expect night-into-day 1/1000" shots with no noise out of any camera. the d7000 is a generation old but it really is still a good low light performer (comparatively), and you're not going to get a whole lot more out of the newer cameras. I have both the d7000 and d600. i didn't really notice all that much difference in noise performance. fix your technique, fix your processing, get some faster/better glass, use a flash... there's a lot more significant low hanging fruit that you can address before hopping bodies and expecting miracles. I've shot entire events (people shots) at iso4000+ on a d7000 (@f3.2). If you can't make the the d7000 work for you the d600 is not going to save you.
Actually not so. Yesterday I borrowed my coworkers D600 and shot with it all night and the low light performance was amazing,
Much better than that of my d7000. I compared shots side by side and the difference is huge at Anything over 1600 ISO. Seems like in my case the body does make a difference.
Picking one up this weekend.