The system is an Asus A8N-VM CSM using onboard video, 1GB RAM, and an Antec PSU.
I replaced the front fan with a Panaflo 80L. You can see it on the left side of the picture. It mounted in with no problem.
The Antec TruePower 380 was fitted with an 80L in place of the Antec fan.
The rear case fans were removed and every vent hole covered from the inside with packing tape. That includes the lid, sides, and back.
Lastly, I removed the noisiest fan in the system. That being the CPU fan. To provide airflow over the heatsink, I installed an 80L where the CPU duct was (the CPU duct has the same hole pattern as an 80mm fan).
The real enabler here is MiniMyth. With no hard drive to make noise and heat, and no power gobbling video card to create heat, the system is easily cooled with these three very quiet fans.
The system went from being quite audible to being inaudible except when the doors of the stand are open and I listen very closely.