You more or less have to assume they are ALL a bit too noisy, because...
1) the fan runs too fast
2) the fan is badly impeded for airflow
Hence, to get one really quiet, you will have to mod it -- simply -- by at least slowing down the fan, or swapping it out for a quieter, smoother sounding one.
So look for a device that uses a fan 80mm or larger; these are much quieter than smaller fans. Also look for relatively easy access to the fan.
This IcyDock is good if a little pricey, with easy access to its fan. They probably make a USB3 version now. http://www.silentpcreview.com/Silent_Ho ... de/IcyDock
The Lian Li EX-503 linked by jimbob looks pretty good -- nice big fan -- but the backplane inside, like most, looks like a bad impediment to airflow.