The combination of traditional polyphase filter architecture with a new multiplier-rich FPGA family provides the means to build wideband (GHz), flexible and high dynamic range filterbanks and FX correlators using a small number of commodity ICs. A 2GHz 4k-channel unit, serving as a prototype for next generation ATNF correlators and as an SKA demonstrator, is described. Polyphase Digital Filterb...