Whats a decent YET CHEAP(ish) sound system with optical input?
Decent & cheap do not go together in the world of comprehensible audio. You want a sound system, but I suggest an affordable receiver that has a little more flexibility. See link below. The 2nd link will do nicely for speakers. With those cheap systems what will happen is you will quickly become dissatisfied & will want to replace it for many various reasons. Save yourself the trouble & get something nice from the start. It’s worth it I can assure you.