Not a lot of input is need for this amp - 1 watt in will = 100 watts out. Modulating to 12 watts on AM = 200 watts out of the amplifier.
I actually have set the input deadkey to .5 watts to get the amp to deadkey around 50-60 watts and swing upwards to 200 watts following the 1/4 ratio rule.
Since this amp doesn't require a lot of input you really shouldn't drive them with more than 2 watts input as you'll sound garbled and the life of the amplifier with be drastically shortened. Of course there are always the people that will tell me that they've been running a stock radio with a 5 watt deadkey into their amp for 2 years with no problems and good for them, but it's definitely not what I would recommend.