With all those speaker wire connections, I would double and triple check for some stray strands of speaker wire and correct connections.
As far as getting your amp checked, I would call Rotel and see what/where to get it checked.
I drive my M60s to VERY HIGH volumes at times and have had ZERO troubles with my speakers or amp (Denon 2805).
I posted a similar problem with a friends Paradigms on some other boards and we've narrowed it down to his amp.
Good Luck.

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DON'T BE A DICK.