I was debating the same thing, the D7100 or the D600. I went with the D600 and so glad I did. High ISO is amazing on this camera compared to the D90 and D7000 I was shooting with before. ISO6400 on the D600 looks as good as ISO1600 on the D7000. I find myself leaving the 28-300VR on the camera for shots I would have been using a f/1.8 lens to get on the other cameras. I bought the refurb D600 from Adorama, only $300 more than the D7100 with the Adorama VIP extended warranty. I totally understand now why everyone says go full frame. It is worth every penny.