I agree with all here, making a special nod to JohnK's suggestion. You're probably trying to compensate too much for your lack of a subwoofer by driving your M60's bass very hard. The low end (bass) is the hardest on your receiver's amps. That's the beauty of a sub. First, it adds the low end no speaker can duplicate. Second, it takes a great deal of load off of your amps, almost guranteeing it not have the shut down. Unless, as kcarlile suggested, double check for loose speaker cables. I know when I had my Yamaha it had a sequence that it ran through to check if the speaker wire was connected properly. If it detected a bad connection it would shut the receiver down. So I'd certainly start there. It's quick, simple, and free
And I'd also second that you don't need a Monster Power strip to solve all your problems. Don't get me wrong, I have one. But I don't think that's the "solution" to your problem. You can't necessarily blame them though. They may have just been brainwashed to tell you that as a solution in order to sell more Moster stuff.
Good luck! Let us know if any of those things resolve the issue.
