I actually can tell a difference between 320 kb/s MP3 and FLAC. But, only with good quality headphones on like my Sony MDR-7506s. If it's out of a speaker I can't tell a difference whatsoever. And, rarely can I tell a difference out of a sound system either. Maybe I could if I knew that one was FLAC and one was MP3 and I was trying to compare the two. But, otherwise, I don't think I'd ever notice. Through headphones, though? Yeah, I can tell. It's not a big difference, but the difference is there.