Hi Garfield,
Yeah think 2 Erica Synths Pico drum modules would work as the BIA has good bass/drum and that would not take up much space in the rack since I want another synth voice and support modules, clock source and sequencer. I've heard that Hexinverter and WMD also make superb drum modules. I really only use a bass, kick and clap drum in my music anyways.