Sorry was just seeing this now. Yes I do own a Ferrum stack. The MR sound wonderful with the Ferrum. You see, i have the Ferrum primarily to drive my Susvara. And it drives the Sus wonderfully. I must say it does an excellent job with the MR too. I runnit at medium gain for both the Sus and MR. Listening volume for the MR is at around 10. It highlights the technical side of the MR. Very detailed. Bass is very punchy, extending to the mid base esp when using the original leather pads. I use the MR both with the Ferrum and the Fireflies depending on my mood or the music I am listening to. Somehow I just love the tubes and how it enhances the warmth, lushness and intimacy especially on female vocals of the MR