I currently own a K5 Classic and D600.
I'd go for the K5 if compactness and weather sealing are paramount. The K5 body is really in a different league than the D600 as far as build & materials go. But on the flip side, the D600 is pretty light as far as FFs go. The D600 IQ is definitely a bit better than the K5, though I don't have a K5 IIs. I prefer the button placement on the K5.....for example, the D600 ISO button is on the bottom left. Dumb. I can operate the D600 with heavy gloves...not as easy with the D600 despite being bigger.
Live view on the D600 also REALLY sucks, so if you're using that a lot, you might want to look at another camera. The exposure simulation just doesn't work as well as Pentax and Canon cameras, and you can't change the aperture while in Live View and see the result change on your screen.
I hear the 24-85 kit is decent but not spectacular. Personally, I wouldn't pair the D600--which has a killer sensor--with that lens..you will likely be disappointed. I'd sell it and get some good primes or buy a 24-120 or 24-70. At least you don't have to worry about SDM. Though I haven't been terribly impressed with Nikon's QC either. My recent 16-35 had red streaking when using it for long exposures at night. Still waiting for the replacement (though that has nothing to do with Nikon).
Last edited by sb in ak; 12-23-2012 at 06:22 PM.