Depending on the sound that you are trying to get in your car i would go with some 6.5" alpine, or polk component speakers and for the 3.5" i would recomend the infinity just b/c i have heard them and they sound good to me.
Remeber that eveybody hears things differently and my sugestion is to go with a cd of the music you listen to the most and listen to different types of speakers. Stores will allow you to do this, if they don't then just find another. Also remember that store clercks will push what they think is best or what is comisionable for them. Depending on your budget you could buy it from the store and have them isntall it or go online and install them youself.
Hope that this is useful to you, and let me know if you have any question