I have a (red) D5300 camera for IR only. It has been converted for the purpose. Image quality is excellent and after some practice, handling the camera goes pretty well too.
I had a major gripe with the poor GPS feature, but after Nikon Nordic told me to download and install an AGPS file to the camera, GPS suddenly sprung to a new life and while still is quite slow to get a satellite bearing, it does so in 1-2 minutes compared to 1 hour or more before.
On a side note: your Sigma lens still is 105 mm and you don't get any higher magnification with it than an FX camera would provide. Only more cropping of the frame. However, as the actual field of view is narrower on the DX, it follows that the DX capture will be more susceptible to camera shake (as you already have found out).