Tough call. It all depends on what you're exactly looking for. I haven't listened to the AD-2000 myself, but for friends' comments I believe they're interesting cans nontheless. But are opened so provide no isolation and have sound leakage, which might be factors to have into account.
The DX-1000 are very good cans in the things they do well, but you could find yourself very disappointed if their flaws are in areas that you value most. They're not neutral, they have a clear bass boost from 15Hz (yes they do reach that low and you feel it) up to about 200 Hz, but IMHO is one of the best bass performances at any price. Rather tight, textured, articulated, decently distortion-free, quite clean... it offers a lot of "layers" into the bass notes which will surprise you when listening to familiar recordings for you'll be discovering nuances and information that you not even imagined was there.
But this has a price. The price is that the midrange sounds a bit strange. Warm, pretty natural, grain free and enjoyable, but with a hollowness (and I'm not referring to the "honkyness" that some other mates reported) in its quality which you might find enjoyable or annoying. I find it OK. Compared to the R10's midrange, the DX1000's is flawed, lacking detail, nuances and naturallity.
Their weakest point, again IMHO, is the highs. It's not for their quality, they're decently extended, very clean, smooth (in the polite side of things) and rather opened -which contributes to an amazing imaging, but that will come later- but have no "punch" nor emotion. You hear the highs, you know they're very good quality, but music's pace and rythm comes from the excellent bass performance, not for the snap from the treble percussions. Overall the highs are good enough to render correct timbres to high pitched instruments like trumpets, sax, violins or female voices, but they tend to sound a bit obscure... hard to explain, it's not that you would say the DX-1000 are obscure or dark cans, but they're not lively and shinny sounding. I believe that this impression is not for their having a low quality treble, but for being it a bit recessed in response compared to the bass one. The 10-12dB difference we measured is easily heard.
One of their strongest points is the way the yield the imaging and headstage. It's deep, with lots of layers and space cues, pretty wide (it opens beyond the cans limits around your head), but don't have the airy liquidity of the R10s and the whole sense of "hugeness". OTOH the R10 don't have the same stage depth.
Overall they're very funny and easy to listen to HPs. They make most types of music, provided they don't have excessive, or low quality bass recorded, very enjoyable. It's easy to get used to their sound signature and once you stop realizing the bass is enhanced in level, you have the firm impression that the recordings you're listening should sound that way. An interesting feature indeed. To the point that swapping them to listen to the HD600, R10, K701, your first impression is that those cans have no bass response hehehe.
If you're looking for closed, "fun sounding" cans, which can make enjoyable most of the music you'll listen, the DX1000 might well be "your cans". But if the frequency response imbalance could be a problem to you, maybe the Denon D5000 -I guess modded, hopefully I'll receive my pair to be modded soon- were a safer bet. Both are very comfy too.
I hope this helps. Regards.