We study algebro-geometric consequences of the quantised extremal Kähler metrics, introduced in the previous work of the author. We prove that the existence of quantised extremal metrics implies weak relative Chow polystability. As a consequence, we obtain asymptotic weak relative Chow polystability and K-semistability of extremal manifolds by using quantised extremal metrics; this gives an alternative proof of the results of Mabuchi and Stoppa-Székelyhidi. In proving them, we further provide an explicit local density formula for the equivariant Riemann-Roch theorem.Then (X, L k ) is weakly Chow polystable relative to the centre of K.We shall see in the proof that the converse does not hold in general; the solvability of (1) is strictly stronger than weak relative Chow polystability (cf. Remark 3.11).The main result of [10] is that (1) is solvable for all large enough k, if (X, L) admits an extremal metric (cf. Theorem 2.9). Combining the main result of [10] and Theorem 1.1, we obtain the following corollary.Corollary 1.2. If a polarised Kähler manifold (X, L) admits an extremal Kähler metric, then it is asymptotically weakly Chow polystable relative to the centre of K.This corollary is also a consequence of the works of Mabuchi [17,18,19]. A stronger version of the above corollary was recently proved by Mabuchi [22] (see also [30]).Our second application to stability is the following.