If you have a quiet water cooled system now, the sound generated by the compressor will seem very loud.
If your current system is air cooled with more than 4 120mm fans, the difference in sound is not huge. Phase is louder than air and water, but offers allmost the best performance.
My advice, if you have the means to phase chage, do so, regardless of the sound generated. You will get used to it in time.
I'm also building a phase change rig. Should be done in about a week.
http://picasaweb.google.co.uk/terente.xp/Calc/photo#5055819932878157618
@Yoxxy
Custom made are not very loud at all. VapoLS is not so much loud as it is just annoying.
Why is it annoying? I'm building the phase change system pictured above with it, I find it quite nice. Sound is not an issue. I can get used to that. I just want better than air or water performance.
The case vibrates like hell. 1 Vapo LS and 4 Laing DDC Ultras' at work. Plus 3x105CFM fans.