LoookeI had the Magni (1/Rev.A) and it was horrible. Potentially... Horrible horrible horrible. The modi/magni made me HATE the DT990/600. Proper amp changed my opinion of the headphone; thus my opinion of the dac/amp. I had some input a few pages ago on the subject. If you click my profile and check my post history or whatever the function is called (sorry I'm on my phone atm), you should be able to find it pretty quickly.
edit: looks like they can from a cursory web search..? Anyone used the DT990 with them?