�The 2006 Civic Si Coupe will be the most powerful, fastest and fun-to-drive Si, and the Civic Si Concept set the direction in terms of its styling, package and performance,". In addition to the Civic Si Coupe, the 2006 Civic lineup will also include a 4-door sedan, a 2-door coupe, a more fuel-efficient Civic Hybrid, and a natural gas-powered Civic GX.