Can't hear any mushy transients. Sorry, I do find mids well articulated , textured and fast enough.Your Cons: "mediocre sound stage", if Aria is called mediocre, then most of the other IEMS would fall to sub-par.
Mids: On the frequency chart it is on par with neutral curve, but you can tell from mushy transients of Aria's Mid that the mid is not the strongest point
Treble: I guess we agree that treble is a good sales point, well-textured, fast responding, and decently resolving
Soundstage unfortunately is mediocre but as I wrote not congested so it can handle classical music but not at it's best.
Compare it to the similarly priced FD1 or more expensive iems like the FiiO FH5s or Dunu EST 112 and then we can talk about soundstage.
Come on , it's good but not a giant killer.
$79 well spent with an easy going sound signature to please the majority but not the purist.