I have an ED80 on EQ5 with dual axis drive. You will never get 3min exposure unless you have guiding (not GOTO). After spending few hours aligning it, if lucky, I could get 90s exposure (without guiding). Once I had 2 min but over half of the shots were not good. Even 90s requires luck.
The dual axis drive motors are rubbish for AP. They have large backlash as they have about 100x gearing inside. You press the RA back button on the hand controller and for a good second or two nothing happens... then you see the star moving. Initially I thought my hand controller was broken. I have not tried it but I don't think guiding will work well with them.
If you get EQ5 I would recommend not getting the dual axis drive but to build your own belt-driven drive. Cheaper and much better. I am just about finished making mine, just waiting for a clear night to take everything out and give it a first test. I am planing doing a writeup once I test everything if you are interested.
Another thing is that thanks to the high gearing, even if you build/get a GOTO system for the dual axis drive, it will be SLOWWWWWW. 15min between star hopping SLOWWWWWW.
Make sure you read
this regarding EQ5 and dual axis motors. For GOTO, 1,2,3-star alignment etc I am using
OnStep.
However, if you are after longer subs you will need have guiding. GOTO will only help finding objects in the sky. The cheapskate method is to use a finderscope with a webcam. I have also built one of those but I still have not given it a test. Changing too many things at once...
Anyway, get HQ5 if you can or be prepared to do some work improving the EQ5.
edit:
You can find 2nd hand dual-axis drives relatively cheaply.
Building your system will cost you a bit less than the new dual-axis drive, apart from your time. And you will learn a lot.