An equalizer includes a first feed-forward stage that provides a measure of low-frequency IS I and a second feed-forward stage that includes a cascade of stages each making an IS I estimate. The IS I estimate from each stage is further equalized by application of the measures of low- frequency IS I from the first feed-forward stage and fed to the next in the cascade of stages. The IS I estimates from the stages thus become progressively more accurate. The number of stages applied to a given signal can be optimized to achieve a suitably low bit-error rate. Power is saved by disabling stages which are not required to meet that goal.