Are both of your top fans exhausts? Because they're creating negative pressure, and that's what's causing your dust problem, not your GPU cooler. Try disconnecting the forwardmost of the 140mm fans and see if that helps.
Both top are exhaust, I have one rear exhaust but a rad is covering it, and all three in front are intake.
Probably should of gotten two 120mm fans instead of 140mm, but the 120mm fans where out of stock.
Or what if I replace the three 120mm in the front with two 140mm fans?