Anything with value like amps and speakers you should keep as loaners or for testing or sell it online.

Old control system crap should go in the garbage. Im talking about old touchpanels and component switches and ancient media servers and cd changers etc. Anyone who wants a cheap touchpanel will buy an ipad. No one wants CRT TV's and everyones phone holds more music than the biggest CD changer you have in your warehouse. Junk it.

TV stands and misc brackets and bolts for sound bars and speakers and tvs...trash it. You can spend an extra few dollars a month warehousing it or hauling it around or you can save that money and go spend the few bucks on bolts when you need them.

Old connectors for cable we don't use i usually throw away...assuming we have something new that will work. I just recently tossed out like 10 pounds of 2 piece compression F connectors from who knows how long ago. I dont need them because now i can get compression 1 piece F connectors from anywhere. I will keep any oddball adapters and plugs like 3.5mm to BNC or weird radio shack type stuff. Right angle anything. That misc stuff comes in handy when you open up a camera box (for example) and find something goofy going on.

My boss purged an entire full size dumpsters worth of misc crap a few years ago. We haven't once thought "i wish we would have kept that".