Naekuh: are you sure it's wise to put 4(!) rads one after another? Imho limited air volumetric heat capacity will drag back cooling efficiency. What do you think of placing those rads not sequentially in four rows but rather at angle - as in at eg. front and both sides, so that back is for blowing air out? Or mounting all rads beneath top cover of case and use front/back for blowing air out? Imho by doing that you should squeeze out more cooling performance (not that you lack it ) from same amount of rads.
Of course, using powerful & noisy fans might make your pseudo stacking less bad, but why not gain same cooling performance yet with quieter fans from very same rads?