Any Japanese made surround sound receiver and speakers than you can pick up from a thrift store or craigslist will sound way better than the modern junk. It will have a big, heavy power transformer and linear amplifiers. There will be no internet connected spyware either. If you find one from the 90’s, it will likely have a phono preamp for your record player too.
Yes, a used PC can work great for a home server. Just don’t go too old or it will be power hungry. Obviously you will want one with an integrated GPU to save power too. If you want to run jellyfin, make sure it supports hardware video encoding, preferably AV1 or H.265.