Arc brings a new design and feature set, while the Play:5 is now just the Five.
Sonos Arc - 5.0.2 Dolby Atmos soundbar
Sonos ARC reviews released, links inside : r/sonos
Premium Immersive Set with Arc, Sub, & Era 100
The Sonos Arc is the long-awaited Playbar update with Dolby Atmos support
Review: Sonos Arc is the Dolby Atmos companion your Apple TV 4K needs - iPod + iTunes + AppleTV Discussions on AppleInsider Forums
Sonos Arc review: Dolby Atmos soundbar brings big sound
Review Roundup: Sonos Arc is a 'miracle of audio engineering,' and 'best, most versatile' wireless soundbar - 9to5Mac
Sonos Arc review: An upgrade worth the wait
Meet Sonos Beam (Gen 2)
Sonos Arc review: An upgrade worth the wait
Sonos Arc soundbar launches with Dolby Atmos support
Sonos Arc soundbar review: Sonos' best bar yet - Reviewed