Over three decades, restaurateur Steve DiFillippo has built a strong brand for his small chain of high-end Italian steakhouses—and for himself: DiFillippo enjoys a reputation as a local mogul and frequently chairs philanthropic events attracting business leaders and Boston athletes alike. Unsurprisingly, Davio’s still fills its spiffy dining room with movers and shakers making handshake deals over a three-course “power lunch” menu that, at $25 per person, comfortably fits any expense account.