Please excuse my ignorance, but how do I know that I need to get the BHA-1? Why not use the headphones socket on the BP26?
Like regular systems (speakers, amps, preamps, etc.) headphones come in different flavours and different sounds. Wilson and PMC speakers have different sounds to them, as do Bryston amps vs. MacInntosh amps. Grado headphones sound very different than Sennheiser headphones.
When in comes to headphone amps, they generally sound very different than the sound you get out of a headphone jack, and people have different tastes in both headphones and amps. Generally, headphone enthusiasts prefer headphone amps, which usually have greater power than do headphone jacks, which are especially important when driving planar headphones, which are increasingly popular. Most very serious headphone enthusiasts seem to prefer tube amps.
But sometimes, as I have discovered just this week, there are some headphone jacks that are can sound better for your preferences than a headphone amp. It turns out that receivers and integrated amps from the 1970s and 80s, because they were built differently then, can have outstanding headphone jack performance. I am now using a Pioneer SX980 receiver built in the 80s that gives me the sound I've been looking for with my Audeze LCD-2 planar headphones. Great detail, transparency and slam, while bringing out their high end. I find that does not have the dry and analytical sound that can come out of solid state headphone amps, but is not as dark as the hybrid tube amp I have used.
Or to put it another way, the headphone hobby is kind of like a parallel universe to the standard audio system, with many different strokes for different folks.
Bryston is new to this very different universe with the imminent introduction of its BHA-1 headphone amplifier. No doubt it will be excellent. But the question will be whether it will be welcomed by headphone enthusiasts, and if not, what other potential customers will embrace it.