It really isn't that simple, however. A number of cars suffer from an issue where the sample simply does not sounds like the correct car, or even much like a car at all. Examples include the Murcielago, Aventador, Ferrari FXX, BMW V12 LMR, Toyota GT-One, the Corvette C5-R, among hundreds of others, which use either the wrong samples or something unrealistic and highly synthetic sounding. The best sound system in the world can only reproduce what is programmed into the game - if a V12-engined car, like the Aventador, is programmed to use the V10 sample from the Gallardo (which it is), it will always be wrong until the developers change the samples. Please go and try the cars I've listed, and you will find that your high-quality reproduction equipment will not help a great deal.
Furthermore, a recent stint on GT2 proved to me that the sound samples used for some of the Nissan Skylines are identical to those used for the same cars in GT6 - these are sound samples that are in excess of a decade in age, designed for a console with 3.5MB of RAM. I can only hope that a sound update is in the works, because they ought to be far more detailed and realistic than they are presently.