Having gone through the 80ED to a 120ED and now back to a 80ED and wishing I kept my 120ED
I can say that the jump up is well worth it. I absolutely loved my 120ED, for NB imaging it worked very well (Since that's all I do really). I also have the 8300-sensor and at 900mm most nebulas fitted perfectly, and with the CCDT67 reducer I can make it work as a 600mm f/5 scope
Doesn't have a built-in flattener but even with my FW-OAG-CCD I could still manage 54mm back focus, and the $150 or so Orion flattener works beautifully with any of these scopes you're looking into.
Of course people will say the spot sizes are different and CA isnt great and built quality is ok and focuser is poor and the rest of it, but I found with a baht. mask the single speed was more than enough. Besides, for NB the CA isn't all that important. It worked fine with my setup which is similar to yours.
What I'm getting at is that it doesn't have to be an expensive triplet or quadriplet (like my old AT65EDQ) to get great images. If you're willing to look second hand then a doublet 120ED or similar with flattener will run you well under $2k with money left over for other goodies. I got my 120ED for $1.1k shipped from brisbane
As Bo said NG are good manufacturers (look up Scagman, he owns one) but any of the other synta-made scopes are pretty good. I've had 4 different skywatcher doublets and all have worked just fine (Yea I know, I used to be a scope hoarder). Goodluck!