The dash speaker is great for acting like a dual channel center surround like most modern cars, without the Dolby theater stereo.
Each speaker manufacturer has their own unique sound, so purists will try to stick with the same brand throughout. It can be a slight noticeable difference on the mid and high notes, but put the roar of the open road into the mix and it usually gets drowned out. And housings will also affect the lows and mids, so pre made sub housings are a big help, being they are designed for the speakers specific Q number to optimize the sound. Speakers will say their frequency range but only if installed in a proper enclosure space. Like most 6x9s are designed to set on the back deck of a sedan and use the trunk as their enclosure.
