Honestly, the solution is a coloured amp. Even though that goes against objectivism, an amp with body/weight to the sound and a bit of bass emphasis can really fix the sound of pop and other exciting genres.
My Nuforce HA200 made the HD800 lose soundstage width and made the sound a bit too forward, but it added the perfect amount of body, bass, and soundstage depth... so for me it is now enjoyable for all genres. Of course it took away some of the good about the HD800, but it more than made up for it by fixing it's flaws. I never found the HD800 annoyingly bright even off of my O2, but it is slightly less bright on this amp (probably just due to the increase in volume on the low end tilting the overall frequency response).
Obviously I do find it bright, but nothing to complain about. I noticed a tiny bit of sibilance in pianos and female vocals, but nothing that immediately jumps out (except on awful recordings). I actually have to focus to hear it, I can't imagine being bothered by it. Then again, I'm bothered by the 10kHz peak on the HE-400 which many people aren't.