The speaker in the 6400/6500 (I have a 6500/225) is great for deep, rich sounds, but it really isn't that great for higher (or stereo for that matter, being one speaker) sounds. The iMac had a great range, obviously tilted a bit towards the treble, and equally great volume. Personally, if I had to pick one set of speakers to listen to everything in my life from here on out, I'd go for the iMac.