Have you heard them your self?? All I hear is how amazing they are and what not but I don't know if its worth it to buy them seeing that I just bought the Ultra 900's. But if I had any since I wouldnt be here in the first place now would I Will I need to run them with an amp?? 25 Ohm is awesome but I know some still need the amp to clean things up.
I have them myself, but I also have the D5000 & D7000 and started listening to music when 78's were still common. So what I might do probably is not the best indicator of what is best for you to do. I also get my pair not long ago for just over $200 shipped.
The D2000 have the best bass and sub-bass in their (former) price class. Further I like them as a non-basshead. I have never heard the Ultra 900 and have not had much interest in the Pro 900 because the reviews and discussion of it indicate (at least to me) that it, unlike the Pro 750, is a basshead can--and an expensive on at that.
The D2000 does not need an amp, but will benefit from one. Unless I'm on the road I always amp. In any case, the D2000 is not a good can for on the go.