superman is on the right track with JL, its good stuff.
my uncle owns a car audio/custom home entertainment shop and i worked for him a few summers ago. ive had great luck with JL and memphis audio in my vehicles.
just a sidenote, do yourself a favor and don't buy them from walmart or the like. like lots of walmart products, it may be the same model, but not the same quality. walmart and big box stores have so much buying power that they dictate to the manufacturer how much they will buy a certain model for and the company has to oblige by cutting corners on production for them to make money. this is true with lots of items there, i just know from installing them that the audio equipment is not the same quality. its a good time to SUPPORT LOCAL.
look in to some Memphis Audio speakers, they are crisp and priced well. JL or Memphis for woofers.
lastly, if you dont plan on installing yourself, try and buy the stuff from the actual shop that is going to put them in. nothing is more frustrating then when someone walks in with an awesome "insert crap brand here" subwoofer or remote start they got on ebay and ask you to install it. stereo shops dont make a killing on labor like a mechanic does. let them set up a package that will give exactly what you want.