Be careful with this fan-less machines, I have read horrible story´s about this. Companies just overpriced this systems and what can happen is that you get a unreliable system with BOSD. Then when you put in some fans to get that heat out of the case you get a normal system and all of a sudden your system is reliable without BOSD.
I had a www.deltatronic.de/en/ fanless system that was rock solid. The only problem was that it was extremely heavy. I would have built a http://www.nofancomputer.com/eng/ but got an Intel NUC for half the price. It has a fan but is so small it is inaudible. You can get passive cases for intel NUC http://www.intel.com/content/www/us/en/nuc/overview.html
Why not oil cooled system, if you want to be real cool? You can submerge the WHOLE computer in mineral oil, (except the HD) although SSD is still good to go into the oil.... https://www.youtube.com/watch?v=xwBrCP9B93E If you use a bigger tank, you don't need fans either.... How to build it: https://www.youtube.com/watch?v=xknxQLFWtPs
"Silent" requires greater expense and effort. More practical is a "low noise" computer. The noise makers are fans... video card, cpu, psu, & case... and perhaps the HDD. Some psu fans are quieter than others. Dell workstations don't even use a CPU fan.. and bigger fans usually less noisy than small ones. SSD to replace HDD. Most trading apps have the computer running at near idle speed, so water cooling should never be much of a consideration.
I agree. If fanless were a real solution, silentpcreview.com wouldn't have a whole site dedicated how to silence a computer.
Video card fan is near silent at idle, cpu fan idles down to around 1000 rpm, psu fan stops at idle usually, and case fan is also around 1000rpm on my corrent setup. Hard drive is SSD. So near silent as it is for trading. Problem? If I load up anything cpu intensive, the cpu fan spins up. If I load up anything gpu intensive, gpu fan spins up. Either load causes all notion of a silent computer to be gone. Trading doesn't cause a load enough to cause noise though. So the real problem is I'm using the computer for other things as said above. Then it gets noisy. The solution to my problem is outside the scope of this forum, as a couple people have pointed out. Since traders don't use their computers for anything besides trading... apparently. I've always used my trading computer for many other things, I don't run multiple dedicated computers. I know it has risks, but I don't like to have a lot of pc's under my desk. Water cooling is the first reason I've had to separate my computers, since it's a risk to water cool. I'm sure nobody wants to hear about it... but I'm still considering all the problems with water cooling, including using ugly hoses from an auto parts store with hose clamps I can crank down to stop the risk of leaks. But that appears beyond the scope of this forum, as no trader needs water cooling for trading uses.
RE: silent the PC isn't there something like active noise cancelling technology you can use - like those used in high-end automobile. Install a microphone, software, maybe dedicated speakers, to supress the noise volume? Via USB or something?
http://www.matrox.com/graphics/en/products/kvm/extio/ Thats 100% silent. They got a model that supports 4 monitors too. Its a bit pricey tho.
If you really want silent IMHO the best option is a thin-client solution. Put a big old beast in a telco or climate controlled room (or shoved in your basement somewhere) and run hardware or software PCoIP or RemoteFX and use a thin client. No noise, no heat, not even that much more of a cost increase.