ehume's suggestions are good.
I would use faster case fans with motherboard and possible GPU automatic speed control on them. That way they will spin at low speed unless system is working hard.
I would probably use a TRUE Spirit 140 rev A or one of the Machos' like Ciarlatano suggested; Macho rev.B, Macho Direct, Macho Zero, Le Grand Macho. Some come with TY-147A fan, some with no fan. Using the optional duct from cooler to back vent with good intake fans means they need no fan.
Nanoxia Deep Silent case are quiet too, but I prefer Phanteks or Fractal Design. I have a Phanteks Enthoo Luxe and like it a lots I prefer it to the Enthoo Pro. Most Phanteks cases come with a PWN controlled 3-pin fan hub, which does a good job of controlling the case fan speed automatically. Their stock PH-F140SP fans are a good fan. I've heard the be quiet! Silent Base 800 is good too.