So, lets say I wanted to do something similar, because of saving on heat and power....in that case, what would you recommend?
First, power savings are minimal in practically every situation for a small system like this so I wouldn't worry about saving power right now however if/when you want to build a large fast system then you can worry more about power savings.
heat, noise, power...after all, my lab sits about 3 feet from me, so the more quiet and cool it is, the bette :)
So if your system is going to be near you then your primary consern is noise. Stay away from 7200RPM or higher drives, these things make noise, maybe not too bad when they are new but after a while they vibrate and it can be annoying. The WD Red NAS drives are nice ans quiet. The Stock CPU fan is generally very quiet but if you are using an aftermarket heatsink then use a good quiet one. Case fans also contribute to noise so run them at 7VDC vice 12VDC, they will still pass air and be reasonably quite.
Case air flow and heat are major things to consider. 1) Run air flow in one direction if possible, from the front of the case, across the hard drives (all spinning drives) and out the back or out of the top. You must have good air flow. 2) You may add a side air input fan if you need air to the center part of the motherboard. 3) Tape off unwanted air leaks/paths. You must promote good air flow in order to ensure heat is dissapated properly. Typically the air flow does not need to be moving at a high rate of flow, even a slow flow is better than just some fans shoved in a case with no rhyme or reason. 4) Cable Management: Cables sholdnot be in the way or the established air flow route otherwise turbulance will hinder the cooling performance.
So you cold build up a system and use a few exuahst fans only and no intake fans but you must ensure air only comes into the case in the manner you desire. This will reduce the number of fans you need thus reducing power and noise, but you must ensure proper air flow. On a few occasions I actually made cardboard air vanes and mounted those in my case to ensure each component recieved good air flow. The most complicated thing here was finding a good way to mount the air vanes.