When I compared my 1540 to my Sig Pro, I felt that the Sig had a much better overall tonal balance than the 1540 and probably would be considered to be the more accurate of the two. Isolation is about the same in both but the 1540's are lighter and more comfortable than the Sig. Still, overall, my preference is the Ultrasone. One could probably call the 1540 a more fun phone for casual listening.
I feel that the signature pros provide more detail and clarity especially up top. (from memory)
You could try the Pros our maybe the Alphas...
Been using the Beyer T5ps and... well... if their cost is really $1100+, I can't hear it. Good bass, but poor subbass, pretty upfront mids and upper mids, highs a bit uneven and overall a bright Signature. Good clarity and detail but Highs are just kind of bad sounding to me (as in I prefer the Shures, Alpha Dogs, Sig Djs, Sig Pros, Denon D5000, etc. Etc.)