Or buy a normal tower chassis with 10x 5 1/4" bays in the front. a typical 3x120mm rad should fit in where the 5 1/4" bays are normally placed. My rad is a 3x140mm which are wider and can almost go in there.
If you do it like that, then make the fans push from the front, through the rad into the computer. It give pretty good cooling in the chassis.
This is with the 3x140mm radiator, which is a little too wide to go completely inside the chassis, but your 3x120mm should be fine.
more about it here: http://sites.google.com/site/qwwwizx/watercooling/cooler-master-stacker-830