I think the 6-speaker system in the Focus is horrible. I quickly ended up replacing those speakers with Infinity 6502ix speakers which sound so much better than those stocks. The only rattles I get from my car are from those red light reflectors on the doors from bass vibration; more from the right passenger door than on the driver side door. It's not too bad, but it is noticeable.
2013 Ford Focus Titanium Hatchback | Tuxedo Black Metallic | Handling Suspension | Tuscany Red Leather Interior | Moonroof | MFT/Sony/NAV