I'd add:
- RAM - only use one stick to save a few Watts, even if going for 2GB. One 2GB stick uses the same amount of power as a 1GB stick
- CPU - downclock and undervolt it to save power. Pretty much all CPUs should run at 1-1.5 GHz and =< 1V. Also, if using a multi-core CPU, disable all but one core. And if using a hyperthreading-enabled CPU, disable that too.
- Video cards - downclock the memory to save power and possibly improve performance (depending on model of card and operating system). On a 1GB video card you can save some 20-30W per card, depending on original and final memory clock. To hit optimal performance, you will have to experiment, as the sweet spot can be anywhere in the 180-400 MHz range
- PSU - ignore the total wattage and focus on just the 12V rail. Single 12V rail is the better design for mining, as opposed to multiple 12V rails