I posted photos of my silent watercooled system a while back if anyone's interested - see
http://forums.procooling.com/vbb/showthread.php?t=12419 .
The conclusion I came to was that if you take out the fun/geek factor from it, the major reason for silent watercooling was to deal with the graphics card rather than the CPU (assuming that for whatever reason a passively cooled graphics card doesn't have the required performance).
Accoustically it's well up to SPCR standards IMHO - the only audible noise is flow noise from air passing through the radiator, there is no audible pump noise, fan ticking, gurgling, etc. whatsoever.