For audio, take to a local thrift store or Facebook marketplace or whatever platform is the most used locally and mix and match your own receiver + speaker set. A decent receiver can be found around €50, speakers can be even cheaper. Most modern speakers of some size are decent enough, bought some second hand Jamo tower speakers for 50 for the set(2) as well. Smaller bookcase speakers with minimum 4 inch (if you don’t go for a seperate subwoofer) speakers can be found for €20. You need some oomph in the lower end to get some extra cinema points. Stereo sets are fine, 5.1 is fun but I’d rather have amazing stereo then ok 5.1 , you know?

For beamers, I’d look for a secondhand beamer that was used in business setting.

A clean white wall is cheap en convenient beaming surface, but a good screen will help increase brightness which can often be the most tricky part about beaming at home. But harder to do secondhand.

Sidenote, I almost never save the boxes of stuff I buy, but the tv box gets special treatment in the attic, because in the box it’s very transportable, but without it, I agree, it’s a big hassle.

GL!