Preamp for Bryston 3BST / Magnepan MG1.6QR

I am interested in people's experience with preamps in a Byston/Magnepan setup. I currently have a Bryston BP20 that results in a very thin and cold midrange. I am looking for something fuller and warmer. I have read good things about the Rogue preamps with Bryston amps, but I'm interested in how the Magnepans stir the mix. Thoughts anyone?