ive had he pro 900s + BD cable for about 2 months, about 500 hours burn in. ive had the d7000s for under a week, and well... my signature says it all. the thing that kept killing me about the pro 900s was how incredibly colored the sound was. i'm an EDM listener and that's probably 70% of what i use my headphones for, 20% for gaming and 10% for tv. with the pro 900s, i found myself really enjoying them for most of my EDM, but when it came to any other genre, gaming, or TV, i'd put the 990/600s on for their more natural, yet still fun (bass and treble emphasized) sound. the pro 900s were about as far away from an all-arounder that i could think of. their soundstage/imaging is ok for a closed can, but when it came to competitive gaming through the astro mixamp with dolby headphone, i can't relaly describe it other than to say that within 3 seconds i'd ripped them off my head. nothing was coming from the right direction and everything was scrambled. the 990/600s have a pinpoint accurate soundstage. and with the BD cable, the basshead in me was in heaven, but the rest of me knew that, if i could only have one pair of cans... i wanted a hybrid of the pro 900s and the 990s. the d7000s are exactly this. i have no idea how denon's done it. they've managed to keep the same natural, un-colored yet still fun sound from the 990s, as well as having a soundstage that really, truly is mind boggling for a closed can, and combining it with bass response that has 100% of the extension and less boomyness than the pro 900s. like i said before, i'm a basshead, but the pro 900s + BD could be overkill. when i wanted the bass, it was so there and so wonderful. but when i wanted to hear mids or treble, i could hear bass. lots of basssss. hence the constant switching of the cans. now... the d7ks just never leave my ears.
perhaps the best way i can think of characterizing the two is to say that the pro 900s never let you forget you were wearing them, while the d7ks let you sink gloriously into a soft pillow of amazingly accurate, analytical, fun, non-fatiguing sound. the pro 900s are so bright and yet so bassy, so you're hearing some sibilance that makes you wince, bass that blurs your vision and legitimately has me checking to see if my subwoofer is on, and a clamping force that, while not uncomfortably tight, definitely reminds you you're wearing big mean scary headphones, and i could never exactly relax with them on. the brushed metal backs of the cans reflect the metallic quality of the sound (this is the "coloration" that i speak of; some might define it differently) which absolutely makes most EDM sound fantastic, but also has me asking "is this REALLY how that sounds??" far too often. the d7ks... from the moment you put them on, while they aren't an 880 or 990 (honestly, what could match that comfort?) you forget they are there and you wind up with a huge smile on your face because you know, inherently, this is how music should sound. songs that i've listened to 300 or more times before finally sound correct. i know that's about as objective as it gets, but there's a gut feeling that what i'm listening to is truly the purest, most wonderful sound... i could go on and on, but the bottom line is, if you can afford em, even if you think you're a basshead and the pro 990s + BD cable are it for you, the D7ks will probably surprise you in a very positive way. i could definitely keep going, and if there's any particular bits that i didn't mention please ask and i'll do my best to respond.
bottom line: the D7k's sound signature is very very similar to the 990/600s. imagine 990s with more bass presence, extension, detail, and slam, and a bit less treble, and you're there. the D7ks make the pro 900's sound metallic, boomy, and scooped.
