I found a JVC RV-B99 BK powered subwoofer cd system only for 50 bucks by pickup and it sounds really good. Maybe not like the best one for like Hi fi speaker, but i think its impressive to its age ...
JVC SP-WA30 sub woofer speaker | in Poole, Dorset | Gumtree
Vintage JVC- SP-PWA-235 Powered Subwoofer Black
JVC SP-PWC50 Powered Subwoofer Silver 180W From Surround Sound System TH-C50