I see it's been a while since this has been posted, but I just came across it.
Stuffing too many fans in a PC is a novice mistake. There are very few cases in which a PC needs that many fans. Two fans with good airflow will provide better cooling than ten fans with bad airflow. Use one fan in the lower front and one in the upper back. Route all cables so they don't impede airflow. Block large holes in the case (I see open drive bays the picture), as they won't allow the air to flow the way it should. Use temperature sensing fans. Make sure fans are properly secured so they don't vibrate.
The above should make a dramatic difference in the sound output of your computers. They won't be silent, but they'll be a lot better and might not cost you a thing.
Other ideas that may or may not be applicable:
- Turn machines off. Odds are you're not using all those machines simultaneously.
- Put some of them in a closet or other room. Long cables or remote access software will give you access.
- Virtualize. Chances are you could replace some of the physical machine with virtual ones.
- Big slow fans are better than small fast ones, but you seem to have gone that route already.
- Set hard drives to spin down when not in use (saves heat and sound).
- Most of those machines could probably get buy with fanless graphics cards.
- Remove cards that you don't really need (and then block the card slot in the rear of the case, so air flows properly).
- Overclocking is over rated.

If you're worried about CPU temps, makes sure your heatsinks have copper cores and that you use a quality heat transfer compound (artic silver).