It can be run single-ended, but on my BTR5 I need to bring the volume up a few ticks on SE connection vs balanced. It's not that big a deal, just a recommendation of mine.I'm curious what you're running these from that the single ended output is not enough for b2. I guess I could understand somebody saying use an amp for them but to say they should be running balanced seems a bit overkill.
now obviously if somebody has an amp that has both balanced and single-ended outputs in general the balanced output sounds better on most of those amps so you would use the balance output just for that purpose but I would never recommend that somebody specifically looks for a balanced output to run B2
I'll have to do some comparison testing on some other devices.