Hi James,
Have tried the BHA-1 to 4BSST2 combination at a dealer (now own the BHA with the balanced outs as shown).
Great sound, was extremely tempted to buy the 4b in one go!
Only downside is that there is no mute on the poweramp.
You need to turn the device of when using the BHA as a headphone amp.
Cheers,
Bob