The famously split Meg Ryan and Dennis Quaid have sold their 12th floor Fifth Avenue co-op, which they reportedly bought in 1997 for $3.1 million. Built in 1924, the 3,000-square-foot flat has been renovated and is described as ''sophisticated and impeccable.'' All bedrooms have Central Park views. The Upper East Side abode also has a fireplace and eat-in kitchen. Ryan reportedly bought an $8 million home last year in Los Angeles, and is shopping for other digs in the Big Apple, this time in the downtown area. No word on whether Quaid will buy a bachelor pad in Gotham.