I've thought about that some time ago, and I pulled out the AC extension to my car from my house, plug in my Soundblaster 5.1 and well, yes, true, it doesn't sound as nice as in the room. Honestly, at that moment, I juz couldn't explain why. I come to the conclusion because I have 4 speakers concentrated in front of me and 1 sub at the back when I am in my room. In the car, I position it in such a way, 2 front, 2 rear and 1 sub rear.
It was way louder than my Pioneer speakers (juz a pair of 3 way at the back), but the quality it was producing obviously did not come close to my Pioneer.
Get a car speaker for OEM look.
Get a PC speaker if you wanna be.........different.
But I would rather get another pair of 2 way for my front than going for PC speakers.