I would avoid the Quiet Ones from what I've read in the past. Also, another alternative is Ocean Runner, but I'm not sure if they make one in the 1200GPH @ 0' head range. Or, you can always spend a lot more and get a nice Eheim pump. Those are nice, high quality units that are energy efficient and quiet.
I found that the Mag 12 was not that "quiet." The droning and humming gets a little annoying after a while. Also, they add a lot of heat (depending on water volume though).
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32"x32"x20" Cube-ish tank
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