I'd go with the HD800 over the T1 by a large margin. The soundstage is bigger and it has a far more natural timbre than the T1s I've heard. Both the HD800 and T1 have similar amounts of bass to the DT880 though.
For the best bass extension and quality I'd go with the LCD-2s but you might find them too dark compared to your current phones. The HE-6s strike a middle ground but I'm not sure if your amp can get the most of those power hungry beasts so you'd have to check in with other owners. Neither have the massive soundstage of the HD800s though.
Other than Ayreon, which is prog rock/metal, i listen to metal, rock, blues and some classic pop.
So far i dont like sennheiser. Veiled, too slow. Not sure if the HD800 has that same sig. From reviews and posts i figured the HD800 wasnt much of a rock/metal can