Hi My first post here and hopefully useful! I'm currently using a Focusrite Saffire LE which I find is great to use. It's basically the same as the Saffire but slightly different i/o - 6 in/8 out. If I'm right, this covers your needs. It also has midi in/out, but I haven't used that yet as I'm using an old Mackie interface for midi over USB just now. It doesn't come with the onboard DSP (which you can't use just now anyway), but because it doesn't have the onboard DSP, it's slightly cheaper than the Saffire for basically the same hardware. It also sound really good to my ears. Focusrite also seem to be fairly pro Linux from what I read on the FFADO site.