The did a fine job when my PC room was 16C, but now, with it being more like 22C, I had to regain that 6C somehow. Pause a moment and ponder this fact of life. You can meter this by placing your hand behind one and feel the air slipping back out the intake. The thicker the fan, IE 80x32mm versus 80x25mm, the better they handle static pressure, up to a point. Add to that, the fact that it's bad air to start with.
Axial fans propel air in an ever increasing cone with a spiral component to it.
If you look at a thermogram of a heatsink while PC is running, most of the heat is concentrated in the center . With the exception of the Delta FFB812SHE, which employs static vanes to de-spiral the airflow, axial fans put out an air pattern with a hole in the middle. So, I was not living under any false pretense that those 36cfm fans were actually delivering their rating. Nevertheless, I had to get the through-case airflow, regardless of the fans I wound up using, greater than it was. Now, in my 7237, there really was no other place to add additional fans, without cutting holes in the sides, top, or bottom.