If you're not adding an amp for the speakers, and keeping the factory head unit, then you want to match something near the pathetically low wattage of the factory head unit. (UNLESS I'M FORGETTING ABOUT AN AMPLIFIER BEING IN THERE?) I think this is the first time I have ever said; I think the Crutchfield person was wrong, (and pretty sure everyone knows that's me putting myself out there in a big way). You COULD use those speakers, BUT (WITHOUT AN AMP OR HIGHER WATTAGE HEAD UNIT), you are paying more for a speaker that you will never use. If you try to really play it loud with those speakers, you could damage those from being underpowered.
If all you are going to do is change the speakers, then you may as well use almost any $40-$50 set. If you MIGHT want to do anything more than that, then reevaluate your dream build, and plan for as big you might want to go.