I'll share my experience:
I've enjoyed my DNA-1 Rev. A through Magnepan 1.7's for a few years. Last year I integrated a pair of 2WQ subs which improved the sound with robust lower notes.
Two weeks ago I purchased a tube pre made by Don Sachs to replace a passive Light Speed Attenuator. I'm still exploring the difference with tubes, the clarity with a passive LSA is so impressive, but the tube pre has a buttery smooth presentation that I'm almost sure was not there with the LSA. I need more time to compare, this is my first tube experience; not sure my ears believe what they hear.
Anyway, my point is McCormack and Magnepan work well together. Hope this helps.