Haven't you guys seen the spec's that say 10% distortion?
Have you ever listened to horrible 10% distortion? It sounds awful.
The "10W" amplifier produces only 5W into 8 ohms or a little more into 4 ohms with reasonably low distortion when the supply is 12V.
A heatsink is needed if the speaker impedance is less than 8 ohms.
But I think the salvaged speakers will also sound awful.