My real world experience over the last few years with my B1K is this: It's a powerful head, however it seems to me to have less total output than similarly rated heads I've owned in the past. Most notable was the GK MB800 I owned right before buying my B1K. I suspect the sensation of less total output has to do as much with the voicing of the preamp as anything since the B1K feels a good bit wider and less aggressive in the upper midrange than the GK. I previously owned a Genz Benz Streamliner 900 that I seem to recall feeling more powerful than the B1K but also less powerful than the MB800, which again likely comes down to voicing as much anything. Too much time has past since owning my older Tecamp Puma1000, which was one of the old models that used a PowerSoft amp rather than an ICE one, but if I had to guess they'd be in similar ballparks.
The moral of my fairly rambling story is that the B1K doesn't standout to me as being especially powerful given the rating, but it is still more than capable of providing excess power on any gig I've thrown at it. I don't play in mega-loud rock or metal bands, but I've had it pushing a pair of TF112 cabs on a number of loud corporate gigs where the bass amp had to carry the room due to a vocals-only PA, and it performed just fine.