Brian, the M22 and VP150 use the same tweeter, and if the difference is as significant as you indicate I would suspect that one of the VP150 tweeters isn't operating. You mention "test tones"; if you have a CD or other source of, say, a 10Khz tone, play it with your ear to each tweeter. Try putting a pillow over(not touching)each tweeter to see if there's a difference.
Although I'm one of those favoring a M2 or M22 center mentioned by chess,the difference should be relatively subtle. What you report seems to indicate that something is wrong.
