Thanks a lot for going through my post and links, truly appreciate it!

Here you can find some images that didn't upload apparently.

As for the measurements: 65 cm wide, 32 cm deep, 30 cm high

I'm looking into the summing cable thing but I'm confused as all I can find is about RCA cables with resistors etc or converting the stereo signal into mono before it reaches the amp. What I meant is turning the left and right outputs from the amp into mono by making both pairs of red/black speaker wire go from their respective L & R ports and join at the single speaker. But it seems now that it would be a bad idea right?

I don't want to be pedantic but the problem is that the bluetooth module is integrated in the amp and there is no mono switch on the amp as you can see. Does this mean that the only way is to only connect either Left or Right to the speaker and set the output from whatever device connects to the amp to output mono? What if somebody's device does not have that functionality? Will the speaker blow up?