2 ohms is 1/4 the resistance (closer to short circuit 0 ohms) than the 8 ohm speakers. What that means is the speakers should match the head end (they are 4 or 8 ohms typically) in order to "--achieve maximum transfer of power to the matching speakers with less losses in the wiring and connections." Two ohms is probably assuming that you are running two 4 ohm speakers in parallel (or 2 ohms).