We show that the space of subprobability measures, equivalently of subprobability continuous valuations, on an algebraic (resp., continuous) complete quasi-metric space is again algebraic (resp., continuous) and complete, when equipped with the Kantorovich-Rubinstein quasi-metrics d KR (unbounded) or d a KR (bounded), themselves asymmetric forms of the well-known Kantorovich-Rubinstein metric. We also show that the d KR -Scott and the d a KR -Scott topologies then coincide with the weak topology. We obtain similar results for spaces of probability measures, equivalently of probability continuous valuations, with the d a KR quasi-metrics, or with the d KR quasi-metric under an additional rootedness assumption.