Have a look at Fosi Audio. I'm currently using a BT30D to drive the passive speakers from an old Samsung integrated amplifier+receiver+2014-era "Smart TV" type system that died. It only has 1 analog input and Bluetooth, but it looks like they have other products in a similar form factor that can take multiple inputs (e.g. the P4 Mini). I was skeptical but needed something cheap to drive those speakers and am quite impressed.