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Craig,
One thing to consider is that deep sky and planetary imaging are two separate disciplines each with their own technical requirements and challenges. Either the Newt or the ED80 can get you started on both but longer term you would find the need to diverge into a set up that is dedicated to one or the other. In terms of visual observing of planets at longer focal lengths, the 8" Newt would be a better choice.
The native field of view with the Nikon 7100 and either the Newt or ED80 would be such that planetary images would be very small. A 2x or 3x barlow would be required to get a reasonable field of view. This isn't a reason to not do this but is just something to be aware of.
My view FWIW, is to start on deep sky with an ED80. Either the HEQ5 or the EQ6 would do the job though the EQ6 will give you more room for growth so if the budget supports this I would go there first.
Whilst I haven't used the ED80 for imaging I would assume that the out of the box configuration for this OTA will not have a flat field so you will find that the stars on the edge of the field of view will be curved or elongated. For getting started with imaging my view is that this is fine, it may be necessary though to crop out the nasty edges to get a good image. Again, this is ok but good to be aware of when you see the first images rolling off the production line.
As a future growth item it would be good to plan for the installation of a focal reducer which can help to improve the flat field. This also throws in additional challenges with the need for very accurate spacing so no need to go there until the time is right.
There are other issues as well to take into account such as lens mount adapters and spacing for backfocus to be sure that you can reach focus with the camera connected. This will depend on which OTA you go with. It is good to be aware of this now rather than bumping into it later if you can't reach focus with the camera connected.
So there you have it. Good luck on this journey Craig.
Clear skies,
Rodney
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