Why update the rear speakers? Because it is very easy to Do it Yourself. The rear speakers usually cost around $100 (for a good one), and you can replace them in about 30 minutes. The best reason is that you can hear the significant difference right away!

What size are the rear speakers?

My 1996 Lincoln Town Car Executive with Premium audio system has two oval 6" x 9" (the distance between screws are 16.5cm X 11.5cm). You can buy a nice pair of speakers around $100 from a stereo shop or less than that from eBay. It should be noted that the factory speakers aren't that bad, so you'll want to get a good aftermarket speaker so get better sound quality then you already have.

How to replace them

(1) Pry off the grill in the back. There aren't any screws, just be careful not to tear the grille fabric.

(2) Remove the four screws at the four corners.

(3) Remove the speaker itself, disconnect the wires.
(4) Drop in the new speaker. Notice +/- is not marked on it.

(Webmaster note: In 1995, the pinout is:
Right Rear + BR/PK (brown and pink wire)
Right Rear - O/R (orange and red wire)
Left Rear + T/Y (tan and yellow)
Left Rear - GY/LB (gray and light blue))

(5) You can also work on the wires from in the trunk.

What I did not tell you

(1)The speaker has a + and a - connections, I don't really know which one is which one. Even you put the wrong side, it will still play, but the bass will be reduced. Switch the wires and see if bass is increased. When you get increased bass, you have it wired correctly.
(2) If you are the driver, you might not be able to enjoy the new rear speakers very much. It improves the passangers' sound a lot, but not so much for the driver.

About the speaker harness

Some stereo shops have speaker harnesses for our cars, but I just simply cut it and connect it to the new speaker. We're only working with two wires, so it's not that hard to reconnect, but going back to your factory speakers woul require reconnecting the plug, so cut yourself a few inches of wire to spare.