The DT880 are faster, but have a nightmarishly painful treble if you're at all sensitive that way. The 701s are also brighter, have a crisp sound in comparison to the 580s, but are not headache producing (I am sensitive to highs) like the Beyers in my experience. The 701s do require a pretty serious amp, but there are a couple that aren't expensive (the DV 336 and the Heed Canamp, for example) that many report as being able to drive them well. Since both those amps handled my K340s well, it's probably true. I didn't have the 701s and those amps at home at the same time.
I'm currently interested in the AD2000s and trying not to be (I don't need more headphones!). I heard them once a couple years ago, liked them, but wasn't drawn to them. They had a light airy sound to my memory at that time. I heard them recently for a second time, and was totally wowed. The system they was paired with was truly impressive (a R2R with master tapes a Zana Deux), but it gave me a taste on how good these headphones really are.
The RS1s or RS2 shouldn't be dismissed as possibilities. They offer a nice contrast to the Senns. I should state that I've only heard the RS1s, but you could read up on the differences between the two if you're at all interested.