I did an in home audition of the 8001 and 8003. They sounded the same to me. I would bet that the 8004 sounds similar. The 8001 and 8003 lean to the warm side. They lack high frequency detail IMHO. I felt their sound was lacking the sparkle that the 740c and 840c had. Bass did not seem as tight either. I'm not saying that I did not like the sound, it was just that there were better options at the time. I believe the reference series has better sound.