Is a 15W amp loud enough?

Hello there, I'm curious about the sound capabilities of a 15W amplifier. Could you please elaborate on whether this amplifier is loud enough for various settings, like a small room, a backyard gathering, or even a larger venue? Are there any factors I should consider when determining if 15W is sufficient for my needs? Additionally, would you recommend any specific brands or models that excel in terms of sound quality within this power range? Thank you for your time and expertise.