Zeus's vocal strength interests me but it's apparent lack of bass also keeps me away... SE5U seems to excel at both so I keep getting drawn to it. Luckily A18 is not really in the pic as it's not only ridiculously expensive but it seems to have a brighter overall tuning than I'd like, as I get the impression it's more of a V-ish shape, though I do wish I had the Apex module as an option as I listen to music louder than many, it seems.
I guess I'm looking for an XXx shape (or an L, flipped horizontally, then rotated 90 degrees counter-clockwise lol) that also excels at clarity without the lifted treble, while also being versatile, as I can only have one of these (C)IEMs at once. W900 remains a possible option, I think.
I'd recommend the H8.2, Aether, and W900 out of the ones I've personally auditioned. The Zeus's bass would fit your description of a coherent and continuous bass and midrange, and unintrusive treble, except its midrange would be more forwardly placed. I'd call the Zeus's bass quantity linear and natural, but of course, different people have different definitons of words like these.