Argon and neon seeded ITER discharges are numerically simulated by coupling a 1D multifluid model for the plasma core with a 2D model for the SOL-divertor region. The model is fully self-consistent with respect to both the effects of impurities on the α-power level and the interaction between seeded and intrinsic impurities. This interaction leads to a significant change in the intrinsic impurity fluxes, and it is found to be essential for a correct evaluation of the average power to the target plates. Even though carbon and tungsten are the real candidates for the ITER target plates, we have compared carbon and molybdenum plates for two ITER inductive scenarios, due to the uncertainties in the tungsten atomic data. In general, the integrated edge-core scenarios with impurity seeding are more favourable in the case of carbon than of molybdenum plates. However, a high density/low confinement scenario with Ne seeding is found for which the requirements in terms of power to the plate and of power through the separatrix are also fulfilled in the case of Mo. The interplay mechanism among different impurities also holds for He ash resulting in a rather weak dependence of the power amplification factor on He confinement.