Panaflo is quiet, and Sunon can be if you mod the power lines going to it. If you dedicate one normal plug to running just your fan chain, you can adapt the plug to output 7V or 5V instead of 12V. Get your voltmeter out and find out which wires are which. From what I remember, the yellow line is 12V, red is 5V, and both black wires are grounds.
To get 7V, rewire so your yellow is in the normal position, and swap the ground with red wire.
To get 5V, diconnect the yellow wire and run the red wire in its place.
Lower voltages will get you lower airflow, but the slower blade speed will also reduce noise. If you're really worried about noise, get the largest fans you can and run them at slower speeds- that way you still get great airflow while keeping quiet.
To get 7V, rewire so your yellow is in the normal position, and swap the ground with red wire.
To get 5V, diconnect the yellow wire and run the red wire in its place.
Lower voltages will get you lower airflow, but the slower blade speed will also reduce noise. If you're really worried about noise, get the largest fans you can and run them at slower speeds- that way you still get great airflow while keeping quiet.