Rear Speaker Blown!

I have a 1999 Expedition (5.4 V8), my little cousin blew the rear speaker in it. I want to replace it with a better speaker that will give me the same sound quality but louder without adding an amp. Does anyone know what size and wattage the stock speaker is and what do you suggest I replace it with?

Any advice, suggestions, ideas, or info would be greatly appreciated!

Look at Parts Express for an 8" woofer that will handle about 50 watts @ 4 ohm's. That's what I used.