What are the cooling mods intended to accomplish:
Here's a recent comparison of some recently released coolers:
Corsair H50 68.1
Coolit Vantage A.L.C. 67.8
Corsair H70 64.7
Coolit ECO A.L.C. 64.3
Antec Kühler H2O 920 61.2
Cooler Master V6 GT 59.5
Prolimatech Super Mega 59.4
Antec Kühler H2O 620 58.7
Thermalright Venomous X 58.0
Thermalright Silver Arrow 55.8
The author's comments below should be taken to heart if building a new Sandy Bridge based system:http://benchmarkreviews.com/index.php?option=com_content&task=view&id=674&Itemid=62&limit=1&limitstart=5
I think the Silver Arrow represents the ultimate air cooler than can be built and still fit within the constraints of an ATX motherboard and a standard computer case..... It's almost ironic that coolers like this are becoming available just as processors transition to designs that may ultimately render them unnecessary; even overclocked to 5GHz, an Intel Sandy Bridge 2600K doesn't need anywhere near this level of cooling. Still, it wouldn't hurt, and as I noted earlier, there are still CPUs out there that can benefit from it.
In other words, with the top end air coolers being overkill even for heavy overclocks, I think the days of CPU water cooling for all but those who list benchmarks as among their most used programs.