I've used the 200 and 400 models and was perfectly happy with them, the build quality is excellent, which you would expect with eheim and whilst they are fairly quiet, they are by no means silent.
The 200 ran an under gravel filter and an air stone on a 80l tank and had adequate power, the 400 ran 4 air stones on 2 larger tanks.
If your only running one air stone then the 100 model should be sufficient for a 64l tank, but I've not personaly used this unit.
From experience air pumps have improved over the years regards noise levels, but expect to hear some humming, placing the pump on a kitchen cleaning sponge or similar will help dampen the annoying vibrations that they all seem to generate.
Again the above is a review, not necessarily a recommendation. Amazon product