One more thing, don't pay attention to people who try to convince you that any one brand/type of speaker is absolutely better than everything else. I've had this argument with people about headphones (sennheiser ftmfw, btw). It really, truly depends on a variety of factors. What music do you listen to? How much of a bass-head are you? Are you willing to sacrifice a little clarity for a little more "thump"? I can promise you that whatever setup you have that masterfully & accurately reproduces classical music in your VX....will probably sound mediocre if you play dubstep or thug rap....and the inverse is also true.
My advice for this is to pay attention to the frequency ranges that speakers can reproduce. This is where components & 2/3 ways really do great, because you have multiple speakers which are each handling different frequency ranges--rather than trying to force 1, single 5" speaker to push everything from 15hz to 25,000hz. At a basic level, your sound system should have a variety of speakers that can each handle different, overlapping parts of that frequency range--without gaps. That's what I'd aim for first. It gets very complex from there, trying to balance the soundstage so that all soundwaves reach the listener at the same time (which also varies based on which seat in the vehicle is occupied).