Does it have a lot of noise? I prefer to not use with an amp as my portable amp is heavy.
No, it doesn't. I'm using my 920 with 3 different pairs of headphones (AKG K450, B&W P3, Beyer DT990) and I am quite happy with its sound output. Loud enough to drive even the DT990 without an external amp.
I used some Koss earphones and it has really good sound. No distortion and the equalizer gives a lot of presets. I don't like "Dolby", makes it sound like the music is echoing. Other than that, it's way better than my SGS II.