'Any idea why these speakersxare rated either 80-200 or 80-400WPC on various ML documentation. That is a significant difference !'
Being concerned about the speaker power ratings is probably the least of your concerns, since your preferred listening levels never reach it's claimed output specs.
You have an older model ML as others have mentioned. Maybe time for a tune up, or upgrade to newer model/brand, or something completely different.
The amp suggestion was a reminder that what amp is driving your speakers also makes up for what the fuss is all about with panels.