Thank you, I appreciate the compliment, but many people had the Pro 900 long before I did, and many other people will have it longer (I've recently sold mine).
The Pro 900 are probably the best choice for you. They have awesome levels of bass, but not in a bad way; never does it make the music muddy, and never does it sound out of place (assuming you listen to them expecting that much bass, otherwise, the bass would easily seem overpowering). They play Electronic music with an incredibly fast and authoritative presence, and they even do other genres like Metal and acoustic justice.
The Denon's bass, while not as powerful, extends just as deep and has a satisfying "subwoofer" feel to it. Even though it is quieter than the bass on the Ultrasone, the bass of the D2000 constantly tricked my brain into thinking a my sub was actually on, a pretty cool affect. For sheer bass volume and speed, however, the Pro 900 easily wins.
They are both great headphones, and in my opinion, the only determining factor on which one to get is the listener's musical preferences and how he/she likes their bass served.
Pro 900: HUGE bass, primarily listens to Electronic music
Denon D2000: Strong, deep bass, great with many genres.
I compared the two and let the Pro 900 go, and I currently own a D5000 and love it. But I will always concede that, for purely EDM, the Pro 900 is the better headphone.
