Just registered to participate in here, hoping it might help the decision of others :)
I was in the business of buying active speakers for pure listening purposes - no mixing whatsoever. After droning a long time over various forums, I set my choice on the CMS65 as I wanted bass to be correct, but didn't want to buy a sub along with it. I coupled those speakers to a Apogee Duet 2, listening from the MacBook Pro.
After a couple of week of listening, I realized that some of some of the songs I used to enjoy "before" on my home stereo (big amp, relatively nice passive speakers) didn't "work" as well on my CMS65 setup. They were missing something. The stereo effect was phenomenal, the clarity of the mediums, the trebles, everything was as nice as expected from the reviews. Pieces of classic music with bass & cellos were awesome, even the bass, so I thought the bass response was nice enough and didn't understand why some songs sounded so empty.
Except I was wrong; The bass response was *not* enough for certain songs. It hit me later when going over "power rock" songs, which are pretty much all over the place spectrum-wise. Those were missing low-end bass!
Pretty much any kind of music with a drum set will sound flat because the kick isn't properly rendered. Take anything below 50hz on a drum kick and you're not left with much :)
So I bought a sub on top of the CMS65 and even though I'm still struggling with the settings because the room isn't sound-proofed at all and I had to put the sub in a corner, now the kicks have power, and a whole new range of the spectrum came to life. It *really* makes a difference.
I just wish the level knob would go even lower than -24db! I don't even understand who would be able to listen anything with it set to max (0 db). I have to set the LO PASS knob lower than I'd like in order to maintain the output level in check.
When you realize the amount of air that is moved by the sub speaker (high excursion means the membrane *really* moves a long way) you understand that even with its 6.5" speaker, the CMS65 just can't render those low frequencies. And those low frequencies are critical to bring life into a drum kick.
Wish I had known that before, I would have gone for the CMS40 or 50 with a sub instead of having those monsters on my desk :)
Hope that helps.