that would be a negative air flow.
you have the 3 120's pulling out the case (+ 1x140mm out depending on your psu orientation.) but only 2 in., that would make your case a negative pressure environment. basically turning your case into a dust magnet as dust will climb in to the case through every seam and vent.
if you want to stick with the x3 120's@40cfm then get x2 70+cfm front fans..
this will turn your case into a positive pressure environment for the most part and only when the psu fan kicks in would it become a negative environment, but to a much lesser degree than your previous setup.
with this setup you should in theory have an optimum air flow setup. positive pressure at idle. and negative at load.
you get the benefits of both setups.
minimised dust due to positive pressure at idle.
and the better heat dissipation of a slightly negative pressure case at load