It's the same concept used for custom chilled water systems, with liquid temps in the sub-zero range. If you got a system that could handle your heat flux input and hold the temps to 0C or below, yes, it would make a significant difference - the difference being that between a few degrees above ambient and what that chiller could hold the liquid temps to.
The question is really - is it worth the expense of those chillers for the difference? I would tend to think a pre-built like those would run in the 750 to 2000 range based upon similiar systems (for example, chillers used in the aquarium arena). And for how much gain? 200Mhz on the processor?
In my view it simply isn't worth it unless you are trying to run in the "top of the world" benchmark arena - and even then, there are much less expensive solutions. Heck, a Vapochill is less than that. Unless you are going to roll-your-own water chiller using a low-temp compressor and you are going for the "top dog" OC'ing race, save your money and your time
Spend an extra hundred or 2 to get the top speed processor and a m/b that OC's well and save yourself a lot of $$$, time, and grief.