Well, I decided my initial requirements are a bit silly. Instead of looking for something with nearly the same tonal balance to the D2000s and a different feel, I've decided I want two sets of cans with different approaches, so I can mix and match with my music and my mood.
To that end, I'm looking at clear and detailed highs, with a bright, open sound and an expansive soundstage. So, I figure that Senns would be a bad choice here, and I'm looking at the DT 880/990 and the K701/601 (both brands are listed with what I'm leaning towards first).
I think I'm leaning towards the K701 ultimately, because people here seem fairly evenly divided between them and the DT 880s, and frankly the K701s seem to have a better build quality and are dramatically more stylish. Given that I don't have the opportunity to demo either of these cans, and reviews, taken on the whole, seem to indicate that they both do what I'm looking for, about equally well, I might as well finalize my choice based on construction and visual appeal. Also, I'm a little unsure of which version of the 880s would best fit what I'm looking for, and having only one choice with the K701s makes things a little simpler.