Mathias,
What kind of viewing do you do and what eyepiece/s do you use with the ED 82 A? Myself, I have moved up from the ED 82 A to the ATX 95, which I see as a worthwhile upgrade, but would not have changed scopes to the ATX if the 85 would have been the largest option. The ATX 85 has significantly wider fields of view than the ED 82 A with its zoom, but does not reach equally high magnifications and (assuming good samples of each) offers only very marginally better image quality. The raw theoretical resolution of an 85 mm objective is about 3.6% better than with an 82 mm, but the Nikon's higher magnifications with the zoom more than compensate for this.
For what it is worth, I carry my ATX 95 on my back while biking, using a Cley Spy tripod harness, and I have a heavy tripod too.
Kimmo