If you want to futz about and go down more rabbit holes, consider vintage hi fi components. The glory days of 2 channel stereo were in the 1970s, and home theater was quite the fad in the 1990s to early 2000s. Today many people want invisible lifestyle systems and have no use for the old battle tanks. So, Craig’s List, thrift shops, and second-hand shops can have really cheap stuff with potential. Some are highly respected too. YMMV.