For Susvara I suspect that the M-Field will have enough power to drive them at ear-damaging levels before clipping. Weather they sound "good" is going to be up to the listener.A question if you please. One of the benefits of Mentor was it could properly run Susvaras and Tungstens. Is the M-Field billed as the same?
For Tungsten (SS & DS), we would need to better understand the voltages provided. Here, too, I suspect M-Field will be sufficient, but again, this remains to be seen as I've not personally read any impressions of the combo yet.
I ordered a DS Tungsten back in December so I hope to be getting my pair soon. I also have an M-Field stack on order, and I'll be sure to share my impression when I get them, eventually.