Beyer DT900 VS Ultrasone 900

For starters, the 990s are open and the 900s are closed.  They will have different characteristics.  From what I've read when I was researching the 990s, is the 900 has a little more bass (in the 60-100 hz range) and is perhaps slightly warmer overall than the 990s.  I've never listened to the 900s, so you can tell me to go fly a kite, but that's what I read.  I own the 990s, and I personally consider them to wide open with good detail, but not overly warm.  However, the highs are on slightly on the sweet side rather than bright side.

But if you do the Pro 900, you gotta do the Keesmod