I don't think AMP8 is anywhere near burnt-in at 24h, if you've had ZX2, WM1A or Z you know those capacitors need quite some burn-in time and changes are going to be significant along the way...
Anyway, AMP4 has been my favorite since it was out, followed closely by AMP5 which is warmer but also very dynamic. To me AMP4 is musical with a neutral, lean and clean take. Yes, it's very coherent. But even not burnt in I would not describe AMP8 as clinical although it's true it has more precise imaging other than that I would describe it in terms of tuning as somewhere in between AMP4 and AMP5 (and probably not too far from AMP4S from what I have read). That means musical and organic despite being a great technical performer but I am listening with the Phantom and VE8...
I wonder which IEM or headphone you're running AMP8 with?
I am using Rhapsodio Galaxy v2 as my IEM. One thing I also felt is that the AMP8 has better control on the bass probably due to the higher damping factor. Wish I can accelerate the burn-in process though!!