Water cooling in a rig like your looking at should be done with a case that has it built in.
www.thermaltake.com
www.Arcticmod.com
www.Xoxide.com
However - if you want a "brand" built one - don't go water cooled. Major companies like Dell won't build a water cooled box.
You could always contact Alienware (owned by Dell I believe) to see if they might - as a specialty division they might. But I wouldn't count on it. If you want someone to put the box together for you - and you go water - then you need to look locally for a reputable company that has done it before. Ask for customer references and check them yourself.
Water cooling is NOT just for overclockers. Its more efficient, quieter and cleaner than air cooling. Run a PC for 3 months with air cooling - then open it up and look at the dust. Run a water cooled PC for 3 months and look inside - its all clean.
Alot of people freak out at the thought of water and electronics. The cooling solution is normally non-conductive electrically, is not corrosive, and has anti-oxidizers in it as well. Water cooling is safe, as long as its done RIGHT. And lets face it - cooler temp components are going to last you longer. Do you want to open up your box every month and blow it out? Or would you rather see a gauge (or hear a audible signal) telling you that you need to put a little liquid in the tank to keep it topped off every once in a while?