The wattage depends on the age of the 410HE. Some older ones were 400 watts RMS (and even lower in older models) but mine is from 1997 and it's rated at 500 watts RMS so I would assume any made after that would be the same.
yeah, i thought the older ones only did 200w. whether 400 or 500, the OP's best bet i believe would be to double his cab.