Welcome to the M60 posse!

Thanks for the pictures. You might try to get a bit of breathing room both behind and next to the mains. I recognize that the screen does not give you much flexibility, but you are undoubtedly getting some undesirable early reflections off the side walls. Two other things you might try to tweak the sound a little bit - toe-in the speakers a few degrees (instead of having them point straight-ahead) and install some sound-absorbing panels or material on the walls next to them.

Nice setup!

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