Well, there's always the option of getting an "S" on every level of Driving Revolution...it would take a while to get the Caterham and NSX that way, but the Clio and Trueno would become available rather early on. On the other hand, the R8 would be very difficult to get.
Otherwise...
- To face the R8, use the 2003 R8, or any of the other LMP cars.
- To face the Caterham, try using the M1 Procar, or any of the faster A-class cars.
- To face the NSX Type-R, try the NSX Type-S Zero, or any A-class MR car.
- To face the Renaultsport Clio 2.0, try using a C-class FF, like the Civic Type-R.
- To face the Sprinter Trueno, try a D-class FR, like one of the two Mazda Miatas/Roadsters.