components generally consist of two seperate driver units - mid and tweeter, and a crossover which controls the frequencies that reach each of them ie. the lower frequencies to the mids and higher to the tweeters. components would be more difficult to install but you would gain a greater control over soundstaging etc. coaxials are basically a single driver unit covering all the frequencies, as your going to be mounting them in the parcel shelf id suggest these, as there location behind you pretty much negates any of the benfits of components. its nice to see you found caraudiodirect, its well worth looking for speakers on there too.