I'm a recovering audiophile. I know exactly what an excellent home audio system sounds like, both in ideal rooms, and less than ideal rooms. The reality is that $1000 and an ideal room will provide FAR better sound quality than $10,000 and a typical non-symetric room.
After a great master and good (not great) speakers, the next low hanging fruit (i.e., best bang for buck improvement) to improve sound quality is replacing the room. For most people, that's not a practical option, despite being the most logical next step (if only sound quality is considered). Apple has used machine learning in an innovative way to correct for poor room acoustics. I've been waiting 23 years for someone to provide an affordable solution to the very problem HomePod is designed to address. I don't care about Siri performance in the least, beyond functionality equivalent to a three button inline headphone remote.
As far as stereo sound, a single HP provides up to 7.1 discrete channels in a single enclosure. Stereophonic sound does not require multiple enclosures, only multiple drivers. When AirPlay 2, arrives, two HomePods offer the potential of up to 14.2 discrete channels. Claims that HP doesn't support stereo are wholly incorrect.