I have a Q460 on loan right now. I also have a K430.
Having had the chance to try a whole bunch of mini cans like the PX-100-II, PX200-II, HD25, HD238, all the Koss, PX90, etc. I'll say that the Q460 is the first driver I've heard in a mini can that performs near it's potential straight out of portables. Most others either sound thick with loose/bloated bass, may sound lean and thin, or somewhere in between. Usually you can hear some symptoms of not being powered correctly off a HP out.
Perfectly fine dynamics across the board. Tight, quick, and punchy bass with no bleed. Meaty mids that are neither recessed nor forward and under control. The treble is extended and right on the line between subdued and sparkly.The treble is just there enough to notice and again behaves in line with the rest of the spectrum. Nicely cohesive as almost everything works together/performs at the same level from bottom to top. The bass is the slightly dominant part of the spectrum. Outside in the real world that dominance gets reduced by external sounds and they are well balanced. There is also some play with fit, moving them front or back slightly on the ears, to tweak the balance a bit.
To me, I hear the same driver as the K430. Tweaked however, more powerful magnets maybe, whatever. The K430 takes more volume and is lean in comparison. The right amp and they should sound near the same. The K430 sounds like it needs more power. It doesn't have the dynamics that the Q460 does. The bass fades fast and, like all notes across the spectrum, are not as sharp and tight. The K430 mids are lean as well. The whole K430 sound is lean which makes the treble stand out more. The Q460 fills in everything nearly just right straight out of the same sources.
Don't have a K450 nor have I ever heard one so, unfortunately, I can't compare those two.
