Dantrag, what did you finally do with your system?
I can tell I have a Athlon XP2000+ running @ 2.4 GHz totally stable even leaving it days on without turning off.
I'm using a Thermaltake Volcano 11 Xaser Edition and I have 5 extra fans at 3600 RPM in the case (2 in side panel blowing in, 2 on the top blowing air out, 1 in the back of the case blowing out. plus the psu's 2 fan, ennermax truepower 480W). It's quite noisy, but I keep 37ºc cpu and 34ºc the case. Ambient temperature in the room is normally around 27ºc in the day, sometimes 22 when i plug air conditioning.
I think that you should go with conventional air cooling, moving a computer with a water cooling solution inside doesn't seem to good for me...