Well, can't help you 100% since I never heard the old Cremona Auditor, but I heard the new one AND I heard both old and new Cremona florestander. So I still might shed some light on the subject. In a word: I agree with the professional reviewers. The M versions have more clarity, a less veiled sound, they are more neutral than the old version that was too much on the warm side of things (well imo of course). The new ones are also faster, more dynamic, more alive than the old one. (Again I can only compare to the old floorstander, but having read a lot about the old auditor, I think the comparison is justified). I found the old Cremona sluggish, a bit lustreless and too laided back. The M still is not very forwarded, but more so than the old. The only thing about the Auditor M was that they distorted a lot at high volume levels, so they're not really for big rooms I'm afraid. But that's quite normal and logical.
Hope this helps.