NSC, welcome. First, the odds that you got three defective tweeters in a row are so low as to be negligible. The M60s are rather easy to drive and a 1050 in good condition should drive them to unbearably loud levels and still have power to spare. My thought would be that the one channel of the 1050 involved with the two blown and one damaged(?) tweeter may be defective and not putting out the full power that the other channel is, possibly resulting in clipping which damaged the tweeters. Have the 1050 checked.
