The ED80 you were originally considering is the workhorse of the astro imager. It's perfect for cutting your teeth on and given the number of objects up there that fit nicely into it's field of view, it should keep you busy for a year or so.
Down the track, once you've mastered drift aligning, guiding and processing, then consider your upgrade to a larger scope.
The learning curve for astro imaging is a long and frustrating one. There are no short cuts. Each step must be taken as it is the foundation for the next, and without that foundation, everything crumbles. But if you take joy in the details, and love to fiddle with techy stuff, this is the hobby for you.
