I have used several different brands, and basically it all comes down to the radiator. And bigger is better. The more fans and more surface area, the more it will cool. A pump is a pump, fittings are fittings, and waterblocks are pretty basic. If you do your research and know the basic plumbing, it will all come down to what radiator you use. The smaller compact water units are really no better than air cooling, you really need a unit with 3 120s or more to make the trouble of water cooling worthwhile. I really don't know what is best on the current market, as I've moved to TEC cooling for most of my extreme rigs. If you are just looking for good overclocks, any good air cooler will get you over 4.0 with the D0 stepping.