Without knowing exactly which of these vendor's products you are considering it is hard to offer useful advise. I have limited experience with the Leben integrrated amps and Harbeth speakers, but I did own an Audio Note OTO and JM Reynaud Offrande's for years. Others may disagree, but IMO neither Harbeth or JMR offer tube-friendly speakers.
Admittedly some of the newer JMR speakers (ex: Cantabile Jubilee) list higher efficiency specs but I still would not consider these as the best match for low-ish powered tube gear.
Admittedly some of the newer JMR speakers (ex: Cantabile Jubilee) list higher efficiency specs but I still would not consider these as the best match for low-ish powered tube gear.