i used to use a 4 ft wide 8 ft tall and 20inch deep closet organizer from home depot,pretty stealthly. even with a 600 watt cool tube 445 cfm fan and 2 220 cfm fans going.my land lord would come in and inspect and it looked like an external ordinary closet.its all about hiding your ducting and fans.i placed my fans on top of the box and ran all the ducting through the back then placed boxes in front of the fans so you couldnt see them.