This paper proposes a new double iterative procedure for sum-rate maximization in a Multiuser MIMO system (MU-MIMO). The proposed algorithm is based on joint precoder and decoder optimization involving two different decoding schemes. For that we considered a precoding algorithm namely the iterative SJNR (Signal to Jamming and Noise Ratio) precoder combined with two iterative receivers. The first receiver is the MF (Matched Filter) determining the best direction maximizing the received power for each user. The resulting receiving vector from the first algorithm will be used as an initialization for the second one. The second receiver is the MSR (Maximum Sum Rate) receiver. The selection of the switching point between these two receivers is determined and performed by a dynamic algorithm introducing very low extra complexity. To link the precoder and the selected receiver through the iterations, we use an iterative procedure based on a virtual channel calculation evolving with the system towards convergence. Finally to validate our proposed solution we compare it with an existing MMSE based iterative optimization algorithm. This algorithm is based on MMSE approach for both the transmitting and receiving side. The obtained results demonstrate significant gains without introducing supplementary complexity.