I don’t quite understand the lower price that the SP1 and SP1.7 command. I have the SP1.7 and use it for stereo only, with all inputs defaulting to 2 channel mode. This unit is great.
Comparing functionality to the BP17, you loose the headphone jack and tape loop, but the SP1 gives you a dac should you need it. At a fraction of the cost of the BP17, I’d highly recommend one.