Lots. Let’s break it down: D/A Converter: Modi 3E uses the ES9018 DAC, Modius uses the ES9028. Analog Section: Modi 3E uses the OPA1656 as an output stage, Modius E uses two separate output stages, one based on the LME49724 balanced op-amp for the balanced output, and one based on the OPA1656. USB Input: Both have Unison USB. SPDIF Inputs: Modi 3E offers coax and optical inputs, Modius E adds AES as well. Size: Modi 3E is the perfect size for stacking with our Magni and Vali amps, and Modius E is the perfect size for stacking with Asgard, Jotunheim, Lyr, and Valhalla.