I know a bit about the Audu R8. The base 4.2L version is a normally aspirated V8 used in other Audi RS models such as the RS4 and RS5. Output is around 450 hp.
The V10 version of the Audi R8 shares the same engine as the (VW Group) Lamborghini Gillardo. The newer Lamborghini Huracan shares the Audi V10 and the AWD drive system. Both the R8 and the Huracan have 610 hp engine options.
Decent car? Worth the price?