I have heard the K701, the '05 and '03 version of the DT880 and own the iM716 which is said to be 90~95% of the ER4 sound. I also owned the CD3000 for a few months before ZephyrSapphire acquired them from me. To answer your original question, I think the headphone you want to get is the CD3000, followed by the 03/05 DT880. Get the 03 version if you want a flatter response, or get the 05 version if you want a little more bass thump. I hated the k701, it sounded soo lifeless.
I'd say the iM716 and CD3000 really sound quite close and very nice. The CD3000 is definitely better. iM716 does not go as low in the bass dept. and has a bass roll off.
I'd rank them:
CD3000>iM716> 05 DT880> 03 DT880 >> K701.
I've tried the Denon D1000 too, yucks, it was rather dark (in comparison to the headphones ranked above) and the bass was no where as clean and textured as those. The bass on the CD3000 is freaking clean, textured and awesome and also goes very low when properly amped. I sold them because I went onto the Stax camp which brings even MOAR of this goodness... speed, details, clean textured bass and clarity FTW.