  A dark sector is an interesting place where a strong first-order phase
transition, observable gravitational waves and/or a dark matter candidate could
arise. However, the experimental tests for such a dark sector could be
ambiguous due to the dark content, largely unconstrained parameter space and
the connection to the visible world. We consider a minimal dark scalar-vector
boson plasma to realize the three mentioned phenomena, with a unique connection
to the Standard Model via the Higgs portal coupling. We discuss the important
features of the Higgs portal in such a minimal dark sector, namely the dark
thermalization, collider tests, and direct detection of dark matter. We perform
numerical analyses of the dark phase transition associated with stochastic
gravitational waves and dark matter, discussing the complementarity of collider
detection, dark matter direct detection and space-based/terrestrial
interferometers as a promising avenue to hear and see the minimal dark sector.
