I have some experience with both the Coincident Frankenstein Mk1 and the Lamm 2.1. I did not like the Frankenstein. The build construction was poor and the transformers had a buzzing sound. The Franks were connected to Acapella horn speakers and you could hear the tube rush through the horns. Admittedly, these were Mk1 Franks and the newer Coincident Frankensteins maybe be better built and have a lower sound floor, but I cannot confirm this statement.
The Lamms, were in an entirely different league. Dead quite, well built, and had a very low sound floor. For an 18w amplifier, they sounded very dynamic and detailed. The only thing that I did not like about the Lamms was the price. If you can swing the price of the Lamm, I think it would be a no brainer. Enjoy!