XS Inc., Research Triangle Park, NC, landed $20 million in private financing from the venture arm of Morgan Stanley Dean Witter for expanding the company's XSAg.com Web site. The auction site handles business-to-business sales of agricultural chemicals and seeds, and XS wants to branch into equipment and parts, fertilizer and veterinary products. The company also plans to use the money for an advertising, direct marketing and public relations push. XS launched the site in January and anticipates processing $100 million in sales next year. Thus far individual transactions have ranged from $2,000 to $150,000.