Welcome to the forums Espazito.

If you're not afraid of some basic DIY solution, why not build some simple boxes out of 2x8 or 2x10's and cover with carpet to match your flooring or M50 cabinets? You could fill the boxes with insulation or sand to help eliminate resonance.

Or a completely different solution - use the M50's in a stereo setup in a different room and buy some QS8's as your surrounds?

Cheers,

Dan
On-Wall M5HP LCR, QS8 & EP500 in 7.1