BTW, the Soma Saga disc frame I bought late last year takes 55mm tires (2.17") with room to spare, and has a steel fork.
I had a 520 for many years, back from when it was a made-in-the US lugged frame, and it was a great bike. The Soma Saga is definitely a significant improvement, and the frame with fork was $500, and by building it up, I was able to put better components on it that trek now puts on the 520. So there are other options...