1. A FIR (Finite Impulse Response) filter structure on an integrated circuit device, for processing data samples and a set of coefficients, at an effective filter data rate that exceeds an input/output data rate by a factor, said FIR filter structure comprising: a plurality of FIR filter stages including at a least an initial filter stage and a final filter stage, each of said filter stages having one or more subfilters defined by a subset of said set of coefficients, a first one of said initial and final filter stages having a number of subfilters that exceeds a number of subfilters in a second of said initial and final filter stages by said factor; wherein: each subfilter in each respective filter stage convolves input data with a respective subset of said set of coefficients; and in at least one particular stage, at least a first subfilter in said particular stage includes a plurality of decomposed filters in a first filter order representing said respective subset of said set of coefficients in a first coefficient order, and at least a second subfilter in said particular stage includes said plurality of decomposed filters in a second filter order, different from said first filter order, representing said respective subset of said set of coefficients in a second coefficient order different from said first coefficient order.