Personally I find having a 7ft tall tube with dual shower heads and dual pumps fine, totally sealed and efficent to cool a XP2400 to around room temps (25c~).
At first it was worse than having 8 fans running with the loud water contact at the bottom of the tube, but after placing some aquarium filter media it was nearly silent and just as cool
The tube i used was copper from a industrial supplier. Gave good thermal contact from the water to the outside air.