As a JL-3 owner driving an older pair of SoundLab A1s, I had a chance to hear the Berning in a direct comparison to the CATs into these speakers. The SL speakers are not the easiest load out there, but they are not the most difficult either. The Berning did fairly well but as expected, it lacked the ultimate control on the bottom end. The top end was a bit soft too vs. the CATs extension here. The CAT had a bigger and more open sound, a little more fullness but otherwise the two amps had a similar tonality. All was fine with the Berning until the volume was turned up to the mid 80s db and more.....then of course the Berning crumbled.
Tubegroover's advice is good: contact Merlin to get a feeling if the Berning is suitable for these speakers. The amp->speaker interface is critical; these should always be purchased as if they are one.
if, I did not find the Berning to be a step down in any significant way.
If you are running the JL-2 with stock small-signal tubes, get those horrible things out of there! With some time and effort, a number of tubes in the 12ax7, 12au7 and 6922 sockets can take the CAT amps to a whole new level, particularly in dynamics, resolution and portrayal of space. When I did the CAT vs. Berning test, I had stock tubes in the CATs. I am now even more aware of the CATs being in a totally different league with premium small-signal tubes.