"You know," Marc Vetri was musing today. "We've never been able to seat an 8-top at Vetri before."

That soon will change at Vetri's flagship restaurant at 1312 Spruce St., the 30-seat jewel box that sits atop many critics' lists of best Italian restaurant.

Vetri is expanding.

It's going up, taking over the apartment that for decades has benefited from the aromas that wafted up not only from Vetri but from such gems as Two Quails, Chanterelles and Ciboulette.

The opening, pegged for May, will also mean Sunday dinner at Vetri, something that the restaurant has not offered in its 15 years.

In addition to being able to host larger parties, Vetri, business partner Jeff Benjamin and chef Adam Leonti want to use the second-floor space as a private dining room with customized menus.

They also plan to use the space for their own events.

They're kicking around the idea of hosting small concerts with the Curtis Institute; conducting specialty dinners; and having a weekly "aperitivo hour" on Fridays. (Basically, happy hour at Vetri with Benjamin pouring wine and Vetri working the salumi slicer.)

The new space will also have a test kitchen.

The main dining room on the first floor will remain as it is, Vetri told me.

Intriguing development, when you add this move to Jose Garces' plans for intimate dining at Volver, coming to the Kimmel Center a block away.