If you are going to replace your stock speakers in your 06 SES sedan. IMHO buy the JBL P8652 6x8 coaxial speakers. The crossover is seperate from the speaker which is rare and has definate advantages over speakers with the crossover built into the speaker or no crossover whatsoever. Plus you can't buy a better pair of multi-element speakers for the Focus, bar none. www.amazon.com
has them for a little over $60/pair which is a steal. They will fit the front and rear doors. Don't settle for less. I had a these speakers in my 05 SES powered by an Alpine MRP-450 4 channel amp rated at 70 watts RMS and they sounded so natural it was practically like I was listening to a live performance. The Alpine is available from www.onlinecarstereo.com
for $189, yet another steal. If you opt for anything less please don't listen to the 4 6x8 JBL P8652's with the Alpine MRP-450 amplifier. You will wish you had taken this advice and will regret purchasing any other multi-element speaker/amp package. I am excluding component speakers as I listened to various brands and none compared to the JBL's. This is after all given to you IMHO. You will not regret this set up.