Just a quick note about the resistor fix. It won't hurt the fidelity of the 8-track output but it will affect the volume. The resistor is in effect that second 4-ohm speaker that was in the other suggestion. Roughly half of the power put out by the amplifier will be dissipated by the speaker and the other half in the resistor. Since the resistor doesn't generate any sound, that portion of the power is wasted.
If you have the room and the speakers aren't too expensive, I'd go with the two speaker per channel setup. Otherwise, an impedence matching transformer will work without loosing quality or volume.
Best of luck.