not sure what the wattage output is... . but I changed my factory speakers on my 06 model for the same reason... just overall crappy sound.
I called Crutchfield and talked with one of their sales reps... even if you don't buy from them, they can give you some insight as to what to look for in a speaker...
I THINK you would want to look for a speaker with a high sensitivity rating number. I put the Infinity speakers in all 4 doors, not sure about which model, but I remember it was the only Infinity speakers that would fit the stock locations.