If you're planning on integrating the Mother 32, maybe you don't need another VCO, but something simple like an Intelligel Dixie II + gives you a versatile VCO/LFO, or the Make Noise DPO/STO modules. reverb/delay is great to have, whether on the rack or an effects pedal. the 2hp modules for reverb and delay aren't bad for the money/size.