  We analyze the impact of the forthcoming CP-violating observables in the
$B_s\to K^+ K^-$ system, combined with the precise measurement of $\sin2\beta$
, in the extraction of the CKM matrix. Computing the penguin parameters $(r,
\theta)$ within QCD factorization yields a precise determination of $(\bar\rho,
\bar\eta)$, reflected by a weak dependence on $\theta$, which is shown to be a
second order effect. Using the SU(3)-flavour symmetry argument and the current
$B$-factories data provided by the $B_d \to \pi^+ \pi^-$ modes, we complement
the $B_s \to K^+ K^-$ CP-violating observables in a variety of ways, in
particular we find that $S_{KK}>0$. Finally, we investigate systematically the
SU(3)-symmetry breaking factor within QCD factorization.
