I am considering an investment in a few Doepfer a-100 synthesizer modules. I was wondering if anybody else shared the same hobby and if you have played with Doepfer gear before? My current line up I am considering is a VCO, VCF, VCA, ADSR, LFO, and a midi to cv unit. Is there any other modules you think are "essential"? I only have about $750 to spend right now.