The AMB500 sounds nice with a Hathor 1203. I find myself boosting the highs and high mids a bit, though (my ears are used to a Baer ML112). I also throw in a slight cut on the 150 slider. Those ABM e.q. points work well with that cab. The size difference is a bit ridiculous.
I tried finding a micro that worked for me like the ABM500.
Genzler was a no-go (esp. regarding the low-freq. voicing).
I remember the Streamliner being close, possibly the most similar to the ABM with my Baer cabs, but that's a 2-year-old memory.
I did a fairly extensive head-to-head at home with a Mesa D-800 and the ABM. I did a few shows with the Mesa before selling. The low-end of course isn't identical, but with the Mesa dialing in enough for me was not problem (plenty of flexible low-end between the deep switch, voicing knob, and eq). The midrange difference was the big standout. I couldn't manage the same frequency peaks with the midrange controls (as the ABM flat voicing--e.q. disengaged). And the Mesa midrange seemed a lot clearer, so much that I thought of it as "dry". Some may like that. I like the semi-congested (harmonic distortion?) ABM midrange. This comparison was all through the Baer cabs. I just don't think those D-800 e.q. centers were a good match for my hands, basses, string choice, and ML112s. It sounded fine, great even, but not what I was pushing for (even though I got sounds from the Mesa that I couldn't with the Ashdown, things I liked more in certain contexts).
Now, the D-800+ I think would do the trick thanks to the flexible mid controls.
FWIW, it felt like I could nail faster sections with the D-800 over the ABM. I am actually considering the + model for my Hathor 1203, you know, in case I get carried away and get a 212--need that 2ohm stability for the 312 stack.
Edit: One thing I remember not liking about the D-800 was my inability to get that thunk and bloom with palm-mute picking. The response time was too speedy--not sure how to describe that. I even tried some compressor tricks. There is just a bit of sag in the Ashdown that I couldn't replicate. And that's important for what I do in my current group.