For much of the ’80s, the CenTrust Tower was the glitzy centerpiece of the Miami skyline. Now the I. M. Pei-designed building has become a symbol of the excesses underlying the S&L crisis. Officials of the taxpayer-backed Resolution Trust Corp. estimate that the CenTrust takeover will cost the American public $1.7 billion. The Feds will consider themselves lucky to recover even a third of the $170 million that CenTrust and Paul - who personally owes the government $30.8 million - lavished on the building. So far, more than 60 potential investors have plunked down $65 for the prospectus; a dozen of them have sent in architects and accountants for a closer look. With up to 85 percent financing available, says RTC official Ed Nutting, “it’s a bargain.”