Just to chime in on the original question. I definitely am aware of the differences between a low bitrate MP3 verses an original CD or FLAC file on my MP3s. A lot of people who only or mostly use ipods and such seem to rip MP3s at 128KBS or so to save space and there is definitely a unique sound verses the original when played on quality speakers or head phones.
I re-ripped all my CDs to FLAC when I bought M60s and also re-ripped anything lower to 256KBs MP3s for my MP3 player. I'm honestly not sure if I can tell the difference at 256kbs. Sometimes I thought I could, but it was questionable and it wasn't blind A/B testing so it may have just been my mind. In any case, I'm sticking with flack for my speaker applications for the peace of mind.
