"Good cans, if you listen to rock/pop"3.0 starson by Yavrey
Pros: Rugged, good lower end
Cons: Midrange deficiency
Summary: I am not currently in a market for headphones; however I was curious about the Ultrasone brand. So I picked up Jethro Tull's 'Thick as a Brick' CD and auditioned $200 HFI-550 together with Bose' $140 Triport (and, yes, I heard all that Bose-bashing). This little review therefore applies to both HFI-550 and Triport.
Headphones were connected to NAD C542 CD player without an amplifier --- don't really think you need one with either pair of cans.
Both HFI-550 and Triport are apparently marketed to younger, non-audiophile consumers. You can tell this based on the styling/design. Both pairs delivered accordingly --- lots of bass, lots of (a bit harsh) highs. A significant feature of HFI's is their rugged build; Triport are decidedly more delicate a thing. On the other hand, my impression was that Triport had a bit better midrange. With HFI's, Anderson's flute sounded a bit metallic; the sound didn't have this taste to it with Triport. Overall, I found both pairs to be inferior in the midrange to my AKG K601 ($280). I got to mention, though, that (a) K601 is an open-back design, and (b) its highs and bass are rather unimpressive.
The bottom line: (a) HFI-550 seem to be a good choice for rock/pop listening; (b) Triport performed equally well, even little bit better.