I have no idea on the 11B, but I do own the 12B since 2009. It's a great piece that only gets better with tube rolling. Most Yaqin gear gets pretty good reviews.
I have an MS-12 and I LOVE it! It is leaps and bounds ahead of a NAD receiver I was using as a pre. Tube rolling is providing some low priced tweaking and fun as well. It is my first experience with tube gear and I am quite impressed. If I had to buy it again (and I would), I would purchase the Grant Fidelity version. If mine ever breaks, I will have a hard time getting it repaired (if i can at all). Unless there is somebody locally (there is) that could fix it. I also run a Maverick Audio DAC through it as well, and i prefer the sound with the MS-12 in the chain rather than straight into the power amp.
**I cannot comment on the MS-11, but i recommend spending the extra to get the MS-12!**