So what took him so long?
"All things have their appropriate time," he says with a laugh. "We're still basking in the glow of our very recent engagement and enjoying that. I'm sure we'll get on with the planning and what-not shortly, but we're just enjoying this experience."
Promoting the next season of the a cappella competition The Sing-Off – which premieres Dec. 6 on NBC – Lachey, 37, said Monday that he did have one ceremony idea: that all the tunes form his former group 98 Degrees "make the perfect wedding songs."
Otherwise, he says, "We're very excited. We're obviously extremely happy and looking forward to everything that the future brings for us, so we are very excited and just enjoying the moment."
Lachey also spoke about his ex-wife, Jessica Simpson, who announced her engagement to former NFL player Eric Johnson just days after Lachey did. Said Nick: "I wish her the very best."