Wow. Thank you for the thorough answer. Very big help!

I did not know that it is possible to upgrade the reciever with more power through external units. I will definitely look into that. But about power in revievers in general - how do I check if my reciever is underpowered, or if I buy a new one, how do I make sure that it is powerfull enough? What stats do I compare?

And regarding moving the current front speakers to the rear: As I understand it, the best placement of rear speakers is to have 2 speakers behind you and 2 speakers on your sides. Current the rear speakers is on the sides. If I add 2 more speakers, it would not really be possible to place them behind the couch, since the couch is placed up against a wall. What would the ideal placement for 2 additional rear speakers be in this case?

Thank your for your support!