To me the versatility of Burmester and how well it plays with other gear is one of it's strong points.
From TAS on the 911mk3: "More interesting yet, to these ears, is how happy it is driving all sorts of speakers, from the ultra-revealing Kings to the sweetly euphonic Coltranes. An amp for all seasons, and virtually all setups"
From Jeff Dorgay's review on the 911: "During the past six months, I’ve had the opportunity to use the 911 MK 3 with about 20 different pairs of speakers, all with excellent results. But the bulk of the review listening was done with the Verity Audio Sarastro II, the MartinLogan CLX, the GamuT S-7 and recently the YG Acoustics Anat II Studio. All world-class speakers in their own right and all of them have given their best performance with the 911 MK 3."
Personally I have run the 911 with PMC EB1i, Rockport Ankaa, and TAD CR1 speakers, all to great effect. Sources include Wavelength cosecant and Weiss Medea DACs run direct to the 911.
Microstrip makes a good point, the balanced input impedance is very low, making it a punishing load to drive in balanced configuration. Unbalanced however almost anything can drive it. My little single ended tubed wavelength cosecant DAC does a fantastic job for example.
I use only a 911 and a 948 conditioner in my setup, everything else is from other brands.