[MENTION=5632]Based[/MENTION]
I just did an entire factory integration system in mine, and it sounds AMAZING (I believe I may be the only member on this forum that has a complete factory integration). Yes, it is more expensive because you have to buy a $600+ DSP (I was able to find a brand new one for $350), but it's totally worth it and you get to retain all the sync/steering wheel and NAV functions. I had an aftermarket head unit and system in my 2011 Fiesta SE, and it's just ugly with the dash kit that they made. Essentially you'll just have a dead LCD screen up top that displays the time. The rest of the screen is non functional. See below image.
Here are some images of my setup. I'm replacing the 2 12 inch subs with 3 ten inch subs in a custom box and adding a battery backup in the trunk.
Brand new speakers in all doors
One amp for the subs, one amp for the speakers, and the DSP