The T1 is more enjotable than the HD800 for everything "involving". The HD800 may be the superior headphone technically, and may even be more refined, but the T1 does a much better job with aggressiveness and impact I think.
I use the Crack with Bendix 6080 and some RCA Clear Tops and I really enjoy it with the T1. I sold the HD800 (which I owned at the same time as the t1) because I much preferred the T1. I also like the Crack more than my DIY Ventus EZ and the Burson Soloist with the T1. I haven't heard the T1 on any other OTL's though, despite attending a few meets.
I'm working on an OTL amp from headwize now, and have designed my own OTL using a 6SN7, 2A3, and a 6080 Cathode follower, so I'm looking to build that next to compare to the Crack. I can post my schematic if you guys want to see, I'm interested in feedback since its my first design.
Anyways, that's just my $.02, that the T1 is better than the HD800 for most upbeat, engaging music.