i was just messing around with my portable player(HTC Incredible), loaded a new ROM onto it so i had to test out the audio. i tried it with my XB500's and then my Brainwavz M2 IEM's and i can no longer really stand the sound of either. both are too bassy and sound so narrow. then just for the hell of it i plugged my HD650's into it. i heard no clipping or distortion, it just didn't get very loud. then i grabbed my old Fiio E5 and hooked that to my portable and the HD650's. it wasn't as bad as i had imagined it would sound. obviously it's no HeadRoom amp, but it wasn't unbearable. it got loud enough as well.
this leads me to ask, what is the portable equivalent to the HD650 that is fairly efficient so it can be run straight out of my portable player? i would use the E5 along with it, but the E5 and other cheap amps like it that aren't solid metal are subject to nasty interference when used with cell phones as sources. so it would be better in my case to use them unamped. i'm thinking maybe the PortaPro's or the UR-55. any other suggestions?