We need the exact makes/models on your laptops especially to know what audio output options already exisit. It would also help to know what other A/V equipment you own. 'Stack of devices' really doesn't help
I have a surround sound system (a stack of devices in entertainment cabinet including receiver and DVD player) that is about 15 years old, maybe more.
I a couple laptops of varying ages; I'm wondering what you think my options are for connecting a laptop to the sound system so I can stream music from the Internet through the big speakers.