I've been listening to my K550s mostly amped lately, and I've had a bit of an epiphany today.
I actually think the K550s sound better unamped, connected directly to my cowon. The mid-high spike is amplified when amped and makes it hard to listen to bands like Radiohead and Linkin Park. Without an amp, the mid-high spike is all but gone and Linkin Park is sounding amazing.
I thought they scaled well b/c I was listening to music they were otherwise good at. Maybe it's my bifrost/asgard combo, but amping the K550s really destroys heavy electric guitar and some drums. Unamped, the balance comes back.
Curious if anyone else had a similar experience.