Well, the way you say it is wrong already, don't become hot because of my statements. Who will not know if add amp, add sub, add some fiber works will be good? Some people will just like a most simple setup by just add a pair of speakers, without adding amp. For some people, they might say that this guy is stupid. But who will sit in that car and listen to the songs? Is he himself, not other people. We can give tons of opinion and views, but we have no final say, the owner will have final say.
Sometime I will sit in my friend's car that don't have amp or whatever, just original HU and speakers. The bass might not be strong as my 12' sub, the vocal might not be so clear/real, but sometimes the most simple setup will be the best. Is something like you everyday eat seafoods, till 1 day you want to eat something simple.