I want to make one hell of a silent pc, and really dunno what to choose between:
NB-eLoop® S-Series - noiseblocker.de/eLoop120.php
bequiet! SilentWings 2 - bequiet.com/en/casefans/259

Both of this fans look really nice and also very quiet. They're making my decision very-very rough, almost impossible.
I think any one of those two fans are good, but if i have to choose only one, whom should i choose?

PS: I will buy 3 of the selected winner and install them on my Antec Sonata II case, 2 intake, 1 exhaust.

Or maybe Corsair SP120 Quiet?

It might be worth considering the Noctua NF-P12 PWM, probably as quiet or quieter than the other two fans you mention. Each Noctua NF-P12 PWM comes with a PWM Y cable, top speed limiting cable and extension cable which would enable you to fit them to your case without buying anything else. This fan is quieter in PWM mode than it is under voltage control. You can chain the fans off your motherboard CPU PWM fan header using the supplied Y cables. The chain will run at minimal speeds at idle and low loads, but will ramp up under gaming loads. If the speed limiter cable (LNA) is used the fans do not exceed around 900 rpm - barely detectable once in a case. Available from sources such as this one.

Noctua is too damn overrated...