Viability for thermoelectric cooling in a computer setting
The "efficiency" for a Peltier as a heat pump is defined by the COP (Coefficient of Performance) which is heat pumped versus power input. This is variable, and at a maximum for very small differential temperatures. Here is an example of a performance curve of COP versus current.


You can see that for a delta T of 10 degrees the COP is almost 3 - at a current that is a fraction of its maximum. More realistically, at 50% of max current you get a COP of about 1.25 so 100W of Peltier input will pump 125W of heat at that temperature differential. You will have to do the sums yourself, but here is a useful article