So will you reject the car if the stereo sounds bad ???
Personally my test tracks for proper hifi are
[video]https://www.youtube.com/watch?v=uv7y6PKEYms[/video]
[video]https://www.youtube.com/watch?v=V-5NnyD8lI4[/video]
[video]https://www.youtube.com/watch?v=nSO6eBeP3uc[/video]
If it sounds good on all 3 tracks it is very likely going to sound good on everything I listen to.
Otherwise Evanescance My Immortal is a pretty good track :
[video]https://www.youtube.com/watch?v=5anLPw0Efmo&list=RD5anLPw0Efmo[/video]
And I noticed that this track is hard for a system to make sound good :
[video]https://www.youtube.com/watch?v=C2ToDJDsNu0[/video]
although the seller might give you funny looks if you play it…