I've been building my system down a similar design goal. Here are some of the various things I've found out.

Gaming aside, my first thought was to by a couple more Macs. Apple actually does a pretty good job on system design, and the computers are pretty quiet to begin with. If my macMini had a solid state drive I would rarely ever here it - the macMini also can't play games. In general, I've found that Complete Silence (~0dBA), Computing Power, and Low Cost are at the corners of a triangle, and, in general, you can only pick two. (it is a flawed comparison, don't poke any more holes in it).

You will never reach complete silence with any moving parts.

Fans can be a big contributor to noise, not just in the obvious noise they make, but in the vibrations they cause in the computer case. You would probably want to pick up silicon/rubber gaskets and mounting hardware to isolate your fans from your case.

The same applies to a hard drive. Some people over at the silentpcreview forums have gone to great lengths to isolate the hard drive from the computer case. Even going so far as to suspend the hard drive with elastic rubber cord to keep vibrations from being transfered to the case.

In general, the larger your power supply is the harder it will be to cool. Even with high efficiency power supplies at 80% - 85% efficiency, when you start talking about requiring 500W - 700W from your power supply unit (PSU) that will probably be putting out about 125W - 175W (at 80% efficiency) to 88W - 123W (at 85% efficiency) of heat. In general, removing this type of heat from a power supply with conventional off-the-shelf PSUs means there will be a fan. (Don't you love the generalities here?)


There are some solutions to the above problems.

The first is to redefine the problem. The problem isn't you need to have a quiet computer next to you, the problem is you need to have a quiet computer. Put the computer in another room. This is Xzin's approach and it works.

Solid state drives will get rid of the hard drive noise (relatively, expensive). Water cooling can rid of some of the need for fans, specifically on CPUs and graphics cards. However, you will probably still want at least one fan moving air thru the case. Water cooling also captures the heat and allows you to move it someplace else (another room, outside, to a loop of pipe buried underground). All these solution will require a pump, the more exotic solutions will require a larger pump - which makes noise. If you thought normal off-the-shelf water cooling solutions were expensive price out what it costs to put 250 feet of pipe 5 feet underground.

Another solution is to not go for complete or dead silence (~0dBA), but relatively quieter. -silencer- seemed to cover these very well. No need to duplicate the wheel.

The solution is another redefine the problem solution. The problem isn't you need to have a quiet computer, the problem is you don't want to hear all the fan noise from the computer. The solution is simple, wear a good set of studio headphones and pump music and the sound output from the game thru them.