The choice between multiple amps and a 5 channel amp really depends on your listening habits...
Th JL5005 is not a very boat friendly amp.. It's power is 100x2, 25x2, and 250 x1... Unless you're running 2 of them and the 25x2 channels power the cabin and bow area, OR you plan to run the amp in a 3 way mode..Highs mids and lows run from each pair of channels...