Ezy , it seems apparent that you have a passion for dso photography , so the dslr is in your destiny anyway
Not knowing alot about the dark side of the hobby (photography), I imagine you would be less limited by the newt/dslr compared to the ed80/dsi combo in the meantime.
The ed80 has a focal length of 600mm, compared to 800mm for your newt, so you would get a 33% wider field but with much slower photon collecting.
Now how much bigger is a dslr ccd chip compared to the DSI ?