I've been using a BHA-1 as a preamp for a while now. It feeds a 3BSST via balanced lines. I'm using the balanced inputs for my DAC and the 3.5mm input for my Echo Show 5. The RCA inputs are free on mine. Anyway. Sound wise, all is good. I don't have a BP-17 so can't comment how they may differ, but I would guess very little. Maybe someone can chime in here.
Functionality wise, there are a few things to consider.
1 - The output of the BHA-1 is quite hot (loud). Bryston offers a tweak where they reduce the output by 12db by changing a few resistors. They charge ~90 for this. I had it done. At a minimum run the amp gain at its lower setting.
2 - You will not have remote volume and mute capabilities. This may not matter. In my case I use the volume on my DAC and rarely touch the BHA-1 volume control.
3 - Don't use standard XLR to RCA adapters on the output of the BHA-1. You need to float pin3 as per Mike's suggestion.
Personally, I am very happy using the BHA-1 as a pre.
Hope that helps.