Looking forward to your impressions
@amartignano once you have the 660S in hand.
I have an idea of what they are going to sound like based on some inferences, I'm familiar with the driver and the HD650 platform. I'm almost 100% positive I'd love them.
I've liked a wide-range of what Sennheiser offers - from HD800, HD650, HD700, HD25, HD250, Amperior, all the way to consumer sets like their new HD4.30, HD598, HD569, HD201.
All of the headphones I listed above are markedly different, and while they have hallmarks of Sennheiser's approach - they all offer something unique.
@Pedro Oliveira, I've probably said this, but if you spot a vintage HD250 Linear for around $125-150 USD (or higher depending on condition) it is well worth it. There are 300ohm and 600ohm (I own this one) versions so both will require some amping though I have no problem with my 02 (configured for higher gain but default should be fine). If you like the natural mid-range of the 600/650 but want more bass and a bit more splash on the high-end, this has it. Think of it as a full-sized HD25 that is spacious, and full-ranged, but has that perfect balance. It is much fuller-bodied than the HD700 and I'll defer it is likely more 'correct' as are the HD650s and likely the HD660S. It actually offers in some way a very spacious and room-tuned experience thanks to its DF tuning. It will be great for the music styles you listed like Ajunabeats and is non-fatiguing. The HD700 I'd say can work very well with some electronic, but you are listening to it at a lower level, fine if you are doing other tasks. The HD700 is awesome, but its hard to say if you'd like it. If you told me you listen to moviescore and classical a lot I'd say go for it. If you want a can that gets you more involved with more beat oriented music the HD250 is it. For that matter is excellent with all music styles and one of my all-time Sennheiser favourites. Would also recommend the AH-D2000 which has yummier bass than the 700, 650, and goes deeper in sub-bass than the 250. I'd also recommend the AH-D2000 and its brethren if you want some real fun for electronic music - it is about indulgence afterall :0
A bit more reference for you Pedro. Listening to Keeno 'Futurist' an extremely well-produced drum'n'bass artist, this track has piano, spacious pads and a very aggressive low-end bite.
HD250 - plenty of growl on the low-end, but it never overtakes the rest. Hats and piano are very clear. Snare room reverb sounds realistic.
HD700 - weird..., okay, can sound hollow coming from the linear 250, but still full. Takes a bit to adjust to the sound. Really opens up, and the technical advances in clarity from that 80s headphone set are pretty clear. Lower-end of the piano has a some real sympathetic resonance to it. Bass is set back but clear. The pads just wash over your ears, and you can hear the faintest sounds against the backdrop. But the HD700 might be a different experience on a tube amp. Myself I prefer my 700 straight, no chaser so solid state is my pref.
Denon D2000 - piano is a bit gelled but has body. Compared to both above, you are already hearing some lower-end sub bass rumbles in the ambience that weren't apparent. Still spacious sounding not like the HD700 and not as realistic as the HD250 but very good. Highs are actually more splashy and livelier than 700 or 250. While the sub-bass is more articulate than either 250 or 700, the 250 actually has a large volume of bass. Though the Denon can arguably be pushed into a basshead territories (it has great power handling where as the 250 can't be boosted) by default tuning it is somewhat light on bass, just very extended (no mid-bass hump like the 650). I'd say just for a relaxed listen, the D2000 is pretty amazing. Absolutely stellar for dnb like Keeno. Back in the day the D2000 and HD650 were oft recommended as complimentary cans and for good reason.
Lastly LCD2 - oh my. See this is why I own all of these cans, but really the LCD2 does a bit of everything from above and with class. I'd seriously consider looking into the LCD2C especially if you want better bass performance from your open backs. For rock, chamber classical, and definitely electronic the LCD2 is incredible. Sub-bass clarity surpasses the rest of my cans. When listening to the drops on Keeno, they just go all the way down into the nether.
But they are currently out of stock. 
