Some time ago I was also in the market for some headphones to accomodate for listening to electronic music. I ended up choosing the dt770 over the 990 or 880 because I really wanted to make the decision to have something different than my HD600; I was really looking to find some closed cans that truly have a different presentation and are oriented specifically towards having some deep bass but are otherwise also just great cans. I didn't think the 990 or 880 were different enough for that purpose so I went with the dt770. I am very happy I made that choice.
I love the DT770 with house music. I listen with them for hours a day. Until recently I had been using the HD600 to do this, but I always felt something was missing. After having used the dt770 for over a month, I am now sure that I feel that the closed back allows for a kind of bass that is superb for beat driven music. It's not about "more" bass; the quality is just more fitting for this kind of music. It hits deeper, makes you feel more. It's way more enjoyable.
I also used to have the HD650, but it's much closer to the HD600 than to the DT770 (obviously). I mean, the HD650 have stronger bass than the 600, but it's ultimately still not adequate compared to that closed back bass of the DT770. The DT770 really gives me that deep rumbling bass when the music asks for it, giving me the ability to sit and listen to mixes for hours on end. The Sennheisers have a sound signature that's certainly gorgeous; they sound very pretty and can make instruments and vocals sound great. But since I acquired the DT770's I don't use the Sennheisers for listening to typical sets anymore. It's just not as enjoyable; the bass just doesn't roll as nicely. With the Beyers, you can really enjoy that groove of the rhythm section with the bass and the cymbals and stuff having such great presence. I can just sit in that and enjoy those beats for hours on end. That is exactly what I wanted from the beginnig but I couldn't find it with the HD600; they were holding back too much with way too many recordings. However, I must say that I do enjoy the Sennheisers with more atmospheric stuff and when recording quality is superb, such as on Joris Voorn's Balance 14, or Jimpster's Amour album, the Sennheisers win out. But this is not very practical for me, because reality is listening to recordings that usually vary anywhere from decent to good (especially with downloaded sets), with only every now and then some recordings that truly make the HD600 sing in comparison to the DT770. Under average and typical circumstances, there can be no contest; the 770 is simply way more enjoyable.
If you do opt for the Beyers, make sure you have a good amp. Get one with a suitably low output impedance so they don't get boomy. Fiio e7 for the 80/30 ohm or Fiio e9 for the 250 ohm would be perfect; plenty of power, very low distortion numbers, no channel imbalance issues, no bloated bass and just great fidelity and enjoyable listening.