Another vote for the Hartmann Onyx. I play a Couf and I find the Carbon and the Hemp are too "much" for the horn. The natural overtones of the Couf are A LOT. The Onyx sound good and allow the horn's overtones to come out, without turning the tone "brittle". Does this make sense?
I should mention that I use Legere Signatures on almost everything else, but on bari I find that they sound: blah... Boring... I love a big, fat, rich in overtones sound on bari. My Durga 3 and vintage Bergs all give me that on all 3 of my baris. But the Legere seems to take away from the tone. Funny that. Since this is not what I experience on any of my other horns.