Should I sell my D600? Locked

Neil the first question you need to answer is why you want a full frame, then you need to ask yourself why you want a fixed lens Sony RX1, then you want to ask yourself why an I not looking at a OMD-EM5 or a NEX-7. Much more versitile than the Sony RX1. For that price you don't get an optical or an OLED viewfinder. Might want to wait for the RX2 if you really want one.  You could always sell the D600 and if you want buy another one when the prices drops.  I hear that they have dropped a lot in Europe, so they might drop in the US.
Take a look here for some smaller and sharper cameras:
http://www.dpreview.com/reviews/studio-compare#baseDir=%2Freviews_data&cameraDataSubdir=boxshot&indexFileName=boxshotindex.xml&presetsFileName=boxshotpresets.xml&showDescriptions=false&headerTitle=Studio%20scene&headerSubTitle=Standard%20studio%20scene%20comparison&masterCamera=nikon_d600&masterSample=dsc_4509&slotsCount=4&slot0Camera=nikon_d600&slot0Sample=dsc_4509&slot0DisableCameraSelection=true&slot0DisableSampleSelection=true&slot0LinkWithMaster=true&slot1Camera=oly_em5&slot1Sample=p1010003&slot2Camera=sony_nex7&slot2Sample=dsc03021&x=-0.20363171683674525&y=0.5107063418488703&extraCameraCount=0