Of course, the K701-2 has a "balanced" sound that works well with various genres, though it shines with classical. With well-recorded pieces, and good stereo separation, the sound strikes a balance between clarity and, for some, lightness.
The D5000 envelopes you in velvety bass, balanced by rich mids. While I don't usually care for the bassier sound, but it has a striking effect: unlike the K701, the Denon can have exciting force. The phones, with rock, have a palpable energy - a vibration makes the phones come alive.
Me? I prefer the K701 style, and cover a variety of genres pretty well. The D5000s are great with rock or any hard-edged music, but not preferred with classical recordings. For harder sounds, the K701 will lack the power for a few recordings, but not too many. In short, it depends on the kind of music you like.
x2 on the music choice. I can't give opinions on the D5000, but the K701 is very bright, especially if you are coming from mostly low end (ibuds, low end sony...) or if you are coming from a sennheiser-type sound with rich bass.
While I happen to enjoy them for most all musical genres, they certainly lack the visceral impact of rock music that most people enjoy, mostly because the bass is pretty anemic. I keep a pair of hd595s for when i care about that. You would need to hear them to decide whether the sound is okay for your type of music.