John Woodard wrote:
If your machine has good airflow around it and runs within the processor/memory manufacturer temperature tolerances you may well not need any case fans and are just able to rely on the power supply and processor coolers.
Although I find that running without a front intake fan and multiple drives can allow the drives to run a bit close to the limit (usually between 55-60C) and if running say 3 drives in a raid 5 array then you can easily go over. So if you elect to do this then watch the drive temps carefully with the smart tools.
Another quick and cheap case quietening tip (even more so if you are putting multiple drives in) is to obtain some "Dynamat" self adhesive sound deadening sheets (designed for use inside cars). I find that a bit of this stuck to the inside of each case panel (you don't need to cover the whole thing just a bit half the panel's size stuck to the middle) removes that biscuit tin quality present in even some of the good cases, quietens down good fans even further and lowers hard drive noise. It also stops case resonance with things like optical drives.
£15-20 gets you 4 sq ft which should be enough to do two computers so well worth it in my opinion.