Since I've had other issues with my focusrite (sudden crackling after some random time... this was on Ableton, not Isadora) and @Fred stated more or less that "the only really trustable interfaces were those from RME", after watching and reading lots of reviews I finally went for RME. They seem to be very praised for audio quality and driver stability. I don't really like the lack of direct buttons or sliders on the unit, but the rest looks really good. I'll be using it with an external MIDI controller such as my NanoKontrol2, mainly because I want to be able to adjust gains "on the run" and want to do this with a physical interface.
I should get it in the next days and will report back.