Actually I bought the machine including a liquid cooling system, since I've become very sensitive towards noise over the years. However, I also wanted to have a very specific (small) case, probably the smallest EATX case that exists.
Oh yes, btw, the workstation is a very decent dual Opteron 246 Machine, with 2GB of DDR400 RAM on a Tyan S2885 mainboard and three SATA drives (of which usually one one is actualy spun up). The system was actually provided by Astaro, since I've complained about their previous way-too-loud Sun v20z test machines that I used to have in my kitchen for some time ;)
Then something unexpected happened: The producer of the cooling system went out of business, and I had to get another one from Alphacool. That system is different to the previous one in that it uses a radiator with two 120mm low-rpm papst fans. The intended original system would have had a totally passive system, no fans at all.
So in the end the system was shipped standard, with air-cooling, large zalman CPU fans, etc. The Alphacool cooling system was DIY and would have never fitted in the case that I chose.
Now, a few months later, I've finally managed to install the liquid cooling system. It required quite some amount of 'case modding', since both the radiator and the compensating reservoir had to be installed externally,requiring some four 12mm holes to be drilled for the tubes, plus an additional number of 20 mounting holes.
I'm very satisfied with the results. The only thing you can still hear is the little noise emitted by the pump. The CPU's are running at 28 to 32 centigrade under full load.