Trouble Finding Regans in Cork

I am researching our Regan family, and I am told that they came from County Cork but have not had any success finding documentation of the origins.  My ancestor Michael Regan came to the U.S. about 1850, and he was born around 1830.  He lived in NY for a short while, but settled and owned land that I believe he farmed in Narragansett Pier, RI.  His wife was Sarah Ann Flynn Regan, and her grave stone states that she was from New Market, County Cork.  I don't know if he was also from there and they came over together, or if they met once they were here.  I haven't found anything regarding her family yet, and what I have found for him is that his father's name was John Regan, and he had a brother named Dennis, whose daughter, Mary Ellen Regan came to live with Michael.  Mary Ellen married into the Egan family, and it appears as though her husband may have come over along with her, so I am thinking that the Egans and Regans were acquainted in Ireland as well.  There is also a Kegan family that shows up in the RI census with them more than once.  The Egan family continued to own the land in RI for several generations, and I believe still owns a few homes on the original property.  Michael and Sarah Regan had at least three children that I am aware of, John F. Regan who settled in Newport Rhode Island, a son named George William Regan, who settled in NYC and is my direct paternal line, and a daughter named Mary Ann, who married Charles J. Weed, Jr.  I believe they went to NY also.  I have more details in my book about the family in the U.S., but I am hoping that someone might be able to help me find my Regans and Flynns in Cork.

Thanks to anyone who can offer some information.