If these lenses took sharp pictures on your Canon. They will work even better on the Nikon D600 due to a much better sensor, number three in the world as to image quality and dynamic range (only D800 and D800E bests it, according to DxO labs).
I am constantly surprised how my older MF Nikkors, Sigmas and Tamrons perform on the D600. It is a quality camera and will serve you well. Right now, you can buy the body and get a free, very high quality AF-S Nikkor 24-85mm f/3.5-4.5G ED VR lens. You won't regret your purchase!
============================================== Darrell Young (DigitalDarrell) www.pictureandpen.com "Better too many words than not enough understanding." ==============================================