The D2000 is a more fun headphone and one my choices for long listening sessions as it is meant for more random genres of listening compared to the K701 and Q701. The D2000 isolate quite well compared to the K701, but this should not be a surprise as we are comparing an open design to a closed can.
I think you should first try a pair of HD-25-1-ii from Sennheiser. They have a similar sound signature to the DT 1350 from beyer and the V-Moda M80, but cost less. They isolate really well for an on-ear design and remain a great pick for a good all around headphone. It may be a classic, but it is just that for good reason.
The great thing and perhaps obscure thing about the HD-25-1-ii is that is has a very different sonic signature compared to the other Sennheiser brethren. The HD-25-1-ii has an up-front sound as well as deep bass impact. Perhaps the imaging leaves a bit to improve upon, but for the price you are going to be hard pressed to find something better.
If it matters I find the V-Moda M80 a slight step up from the HD-25-1-ii, but the differences can be subtle to some.
At the top of this tier remain the DT 1350. They are a very nice sounding headphone. The comfort issues can be remedied with a little adjustment and know how. I ended up not liking the slightly recessed mid-range, but over all they sound amazing.
