Calvindo-
I would also go with 4 but I would go with 900s instead of 1200s. One of the sharks, sorry I can't give proper credit, pointed out the fact that the 1200s don't turn that much more water than the 900s, but they take a lot more watts to run.
MP900 8.5watts 230gph
MP1200 20watts 295gph
HTH-
Jeremy