In this paper, different amplification strategies are evaluated to improve the cost efficiency per GHz (CEPG) of WDM mixed-line-rate networks with 40G/100G/200G/400G in a nation-wide network topology. Significant improvements in CEPG and overall capacity increases can be achieved by the selective placement of additional in-line amplifiers. Placing additional in-line hybrid Raman/EDFA in existing networks can improve CEPG up to 17% and nearly double the effective capacity of the network.