May & Speh Inc., Downers Grove, IL, has acquired the assets of Sigma Marketing Group Inc., a full-service database marketing company headquartered in Rochester, NY, for approximately $20 million in cash. Sigma also received warrants to buy May & Speh common stock in connection with the transaction. Sigma will become part of May & Speh’s direct marketing services business and will be supervised by present management at the company’s Rochester facility. In May, Acxiom Corp., Conway, AR, had agreed to acquire May & Speh, a direct marketing rival, in a $625 million stock swap.