It depends on the wattage of the speakers. General rule is take the lowest wattage and times it by the number of speakers. So if you were running two 30watt speakers and two 60 watts, you would take 30x4.
it looks like 80w per speaker. 8 ohms each.
If paired in parallel that would be 4ohms a channel
does that change the wattage? ohms confuse me....