Kenobi, I listened to the entire system and it is difficult for me to isolate any particular observation to the BC Ref 500 amps unless I auditioned them in my own system. Furthermore, there were no other amps in the same room against which to compare the Ref 500s. I also have no experience with the original Ref 500/1000. Yet, here are my subjective impressions roughly mapped to your itemized issues:
1) Midrange was solid/textured, and transparency was in evidence.
2) Speed -- I call this transient response. . . yes BC seemed quite nimble/agile on macro/micro transients.
3) Laid back? -- System was not 'agressive', I thought it sounded 'realistic' and eminently listenable without ever sounding dull/boring.
4) Smooth -- System did not sound etched in most recordings, but I was very pleased by the amount of harmonic texture that was exposed.
5) Resolution -- Seemed to be one of the most resolving systems at the show. But could not perform a direct comparison with other amps.
6) Soundstaging: broad, deep, and expansive, good 'air' around instruments.
Unles I have the opportunity to listen to BC Ref500 or Ref1000 at some length in a very familiar system/environment, I can't make meaningful comparisons with closely competing devices. . . Yet, it was pretty evident to me after 2 lengthy visits in the suite, even sitting way to the side and at a 90 degree angle to the speakers, that the new BC reference lineup are worth a very careful listen/consideration. G.