The condensation of elementary quanta and their macroscopic occupation of the same quantum state, say k = 0 in some reference frame Σ, is the essential ingredient of the degenerate vacuum of present-day elementary particle physics. This represents a sort of "quantum ether" which characterizes the physically realized form of relativity and could play the role of preferred reference frame in a modern re-formulation of the Lorentzian approach. In spite of this, the so-called "null results" of the classical ether-drift experiments, traditionally interpreted as confirmations of Special Relativity, have so deeply influenced scientific thought as to prevent a critical discussion on the real reasons underlying its alleged supremacy. In this paper, we argue that this traditional null interpretation is far from obvious. In fact, by using Lorentz transformations to connect the Earth's frame to Σ, the small observed effects point to an average Earth's velocity of about 300 km/s, as in most cosmic motions. A common feature is the irregular behaviour of the data. While this has motivated, so far, their standard interpretation as instrumental artifacts, our new re-analysis of the very accurate Joos experiment gives clear indications for the type of Earth's motion associated with the CMB anisotropy and leaves little space for this traditional interpretation. The new explanation requires instead a view of the vacuum as a stochastic medium, similar to a fluid in a turbulent state of motion, in agreement with basic foundational aspects of both quantum physics and relativity. The overall consistency of this picture with the present experiments with vacuum optical resonators and the need for a new generation of dedicated ether-drift experiments are also emphasized.