Hey! Have we met?
This was exactly my conundrum that led me to Head-Fi in the first place. I went with the eQ-7s but have now moved on to a set of AS-2 customs. I can honestly say that I prefer and would recommend Aurisonics over the eQ-7. The eQ-7 has no sense of space or instrument separation. For example, I'm working on Salome right now; I have been listening to the Nilsson, Wächter recording with the Vienna Philharmonic with Solti conducting with my AS-2. Not my favorite Jochanaan, but the recording is solid. When Jochanaan is singing from the cistern I find myself almost turning my head because the sound feels like it is coming from over my shoulder. With my eQ-7 the sound feels compressed and stuck in my head. The orchestra never feels as expansive as it does with my AS-2.
The eQ-7 can also be quite harsh on older recordings. It has the tendency to get pretty sibilant on top and the hiss from a record transfer can really ruin some of the recordings. I have a Tristan from Beyreuth that is almost unlistenable because of the constant record noise that is in the sound. The AS-2 is far warmer and more forgiving of these recordings.
I had an opportunity to listen to a pair of Shure 215 recently. My honest opinion was that they were good, but not on the same level as the AS-2. The sound was bright and detailed, but they didn't have the same sense of space that the AS-2 provides.
I would really recommend looking at Aurisonics. Their ASG-2 is coming out soon and should fall right towards the top of your price range. If you would like to hear the eQ-7 and are in the Philly area in the next couple of weeks, I would be happy to lend you my pair. Other than that, I really haven't experienced the same level of clarity and sound stage with anything outside of a full sized set of orthodynamic headphones.
The only thing the OP should keep in mind is that the Shure 215 is $99 (and universal fit) and the AS-2 starts at $799 and is a custom. That's a pretty big leap from $3-500 although you are right that the ASG-2 would be in their range at $499 and details should be available very soon.
I have heard good things about the AS-1 custom if they would like to jump in but maybe can't afford the upper end model. Your comments about the AS-2 have me really, really excited!!