Big buyout firms like the Blackstone Group and Kohlberg Kravis Roberts do headline-grabbing transactions and collect eye-popping paychecks. But when the economy slows down and lenders turn wary those mega-deals are the first to dry up. Meanwhile the modest middle market -- typically deals in the $500 million to $1 billion range -- keeps plugging along. In fact according to panelists at the 2008 Wharton Private Equity Conference middle-market investors are to some extent insulated from the current credit crisis and other economic ups and downs. ”We’re delighted with the credit crunch ” one speaker said.