I've been looking into sub-ambient cooling for a while but I'm not sure if I'll go TEC, waterchiller, evaporative cooling, or phase change first.
TECs are another science all in themselves and I'm not all that knowledgeable about them, but I know the basics. Lots of math involved and you have to know exactly how much heat whatever you are trying to cool is putting off. The more power you put into the peltier, the less efficient it becomes. These
437W peltiers are what people are using right now for the last couple of generations of processors, and it's starting to get to the point where the heat output by the peltier negates its cooling effect because modern overclocked CPUs put off upwards of 175W. A decent water cooling system will be able to remove anywhere between 500 and 1500W depending on radiator size and airflow.
I do know that waterchillers are waaay more efficient at cooling down your parts than a direct contact TEC. Basically, a copper chamber is machined and TECs are applied to the outside of it. A second water cooling loop is used to cool the TECs. The chamber replaces the radiator in loop that flows through the computer.
Evaporative cooling is essentially upsizing your reservior greatly and leaving the top off. Bong coolers are easy to make, look it up. They are massive and ugly though. Goods points are that it's cheap, bad points is that your loop will gather dust in the water without a filter, humidity in the room increases slightly, and you will never see sub-zero temps.
Phase change is the ultimate solution, but you will pay for it. The really dedicated hobbyists will build their own from old fridges and air conditioning units. A gas (R-12, R-22, etc, depending on what the compressor is designed to run on) is compressed, cooled down by copper coils, squeezed into a capillary tube, meets the cooling block where it expands and boils, evaporating and taking massive amounts of heat with it, then is returned to the compressor. 1/2 to 3/4HP compressors are required, drawing about 400-600W. The compressors are not designed to run 24/7, so certain brands are recommended and the computer shouldn't be on for 12+ hours a day. But man, I would love to see my processor fully loaded at 5GHz+ at -120*C.
Insulation is a must with any of these options. Anytime you have a material that is cooler than the ambient air around it, you'll see condensation, which is bad. Dielectric grease is used to fill the socket and neoprene blocks are cut for around the socket. Not much to it it looks like.
Performance air cooling will help you reach a stable everyday overclock and increase the life of your processor, water cooling is for geeks who want to run unnecessary overclocks for the fun of it or want a quieter computer, and sub-ambient cooling is just for bragging rights.
Imagine your electricity bill in the summer running a 700W load on the computer while gaming, 600W just for cooling, and your air conditioning also running while additionally removing 1300W that the computer is putting into the air. Yeah, I get weak knees.