the biggest advantage of the water cooler isn't that it cools more watts/second in fact some don't disperse more heat/second compared to big towers, it's that it can take the heat outside the case. the cooling chamber being outside it's not influenced by air flow.
in eastern europe the zalman full copper coolers are also priced very low CNPS9700 for example can be had for about 30usd where i leave. i don't get really why they are much more expensive elsewhere but i've set a couple on amd boxes and they work very very well.