I have a Harmon Kardon 3500 which supplies 50watts to 8ohm speakers. I plan to have B&W 705 speakers. The speaker settings are (Headset only, A, B, A+B)
I have read that is safe to connect both A+B to supply power to each speaker respective of left and right, to provide better performance. Also stated was "It is better to leave the amp-reciever set to 8ohms for the speaker setting regardless of the speakers being 8 or 4 ohms.
It's irrelevant if you are only running one pair of speakers. A and B speaker outputs are wired in parallel to the same amplifier channel. Unless you are simply trying to get as much wire as possible feeding the speakers, you have accomplished nothing of any portent in spending money for the additional cables.
If your quote is from the HK instruction manual, I would believe them. That's why they're called instructions.