I have a Gladiator 600, which has two fans. One front 120mm 19 dBa intake (1200 rpm I think), and one top 140 mm 19 dBA exhaust fan (1200 rpm). I want to put a 120mm for the rear fan, but I want it to be veeeery quiet. Quieter than these two I have.
I've used this Scythe before when building a system with the same case http://tinyurl.com/dlhv3x but now it's out of stock! I liked that it was S-FDB.
You have fans running at 19db already, adding another 19db would be fine right? It'll add about 1-2 db to the loudness, but it will double the CFM of the fan you linked above, just saying, it's a better cooling solution.