For actual buying intent (not just firmographics), the main players are Bombora, 6sense, and Demandbase. They track which companies are researching specific topics based on web behavior across publisher networks. Bombora is usually the most accessible for mid-market. 6sense is more enterprise/ABM focused. If you're looking for G2-style intent (who's actively comparing your category), G2's Buyer Intent product is actually decent if you're already listed there. Otherwise ZoomInfo has intent data bundled but it's pricey. What's your use case/budget?