I counted 5 posts claiming one 1x12 radiator is enough to make it all fantastically quiet.
That's because it is.
Athlon 64 X2 4200+
1x120mm heatercore radiator with Yate Loon @ 5V (inaudible)
My CPU and GPU temps never get above 45C, even after several hours of 3DMark or ATITool/CPUBurnX2.
I noticed several people claiming their system is quieter than any air alternative even though they obviously enough keep their pump turned on.
My pump is silent in my case. Eheim 1048 mounted on foam. Tubes are also foam mounted where they touch the case because I found they were vibrating too.
Of course, the system isn't quieter than a passive or single fan air cooled system, but it was also a pretty high end system at the time.
I think you are reading too much in to what people are saying. Sure, air cooling is very good, but ultimately WC can out perform it. If you need that level of performance is up to you, if not you can build a slightly lower performance silent system on air for a lot less money.
I keep reading about fans, on whichever rad, running over 4V and still the owner claim the system is silent or at least quieter than air.
I suppose it depends on your system. I find Yate Loons at 5V inaudible in my two systems (customised server case and P182). The HDDs and the plumbing in my house make more noise.
If you find you need to run your fans at 4V or lower, maybe they are damaged or you are just super-sensitive to noise. I had my hearing tested last month and I'm above average. I am also in to headphones in a big (read: expensive) way so I'm pretty sure my hearing is good.
I generally see no point running my fans below 5V because they are already silent. Actually, in the P182 with WD500AAKS HDDs I can go to about 8-9V before the fans become louder than the HDDs.
I read a lot about GPUs but not so much about HDDs which seems to imply the W/C crowd's computers are not quiet enough for the drives to emerge as the worst noise polluters yet.
Mine are. I used to have Grow Up Japan Smart Drive 2002 enclosures and they still were.
I kept reading "but that can be done by..." but few are actually doing it because it's too damn hard. Believe me when I say pulling off feats like completely dampening a pump isn't coming easy.
I didn't find it very difficult. Mine isn't even the quietest or lowest vibration pump.
I didn't get any reaction to my main concern: the continuing issues of advice to beginners to go W/C for silence. It's folly.
It all depends what your goal is. If you want a very high end system producing lots of heat, WC is worth considering for silence. You could just use air with variable speed fans perhaps, although that doesn't help if you do overnight renders or run distributed computing projects.
For any mid to low end system, air is clearly the way to go.