Earlier in this thread I did a comparison over most of the Adel line. IMO, you'd be best off with the A3. The custom fit really, really helps with clarity (IMO, of course) and also, the universal versions tend to have emphasized mids, and slightly recessed bass and treble, in comparison to the custom versions (That's coming directly from someone who works at 1964). If I recall correctly, the universal version of the A3 was a very good earphone, I'd say it was probably better than the universal V6-s.
I am a very happy owner of the A6, and I love it. I got mine for $900, since I was a bit early to the party, but I would happily have paid full price for them, they are that good.
That being said, if all you're looking for is clarity with bass, and you're okay with recessed mids, then I would suggest the A4 custom. It's the same price as the U6, but still custom, and the clarity in the bass is ridiculously good. It's something to consider. Especially when playing live, I think that a custom monitor will serve you FAR better than any universal would. The comfort is amazing, and honestly, they're much better than the universal versions (imo) as far as sound quality goes.