Yes, changing the front speaker components can improve the sound quality when compared to the OEM pieces. It will depend how well you install the replacements, what speakers you choose, and what sound you're looking for.

The front door panels have to be removed. BSW has an awesome step by step on how to go about removing the panels and preparing the new speakers to be installed in the provisional spot. You will have to use the OEM midbass speaker housing to serve as a mounting ring for your new speaker. That, or make custom speaker rings identical to the OEM speaker housing.

I suggest using some form of sound deadening material around the mounting area of the midbass driver and behind the driver on the inner part of the door skin.

Make sure the midbass driver is well secured and sealed in its new home. Once again, referring to the BSW install file on their site and in the forums will explain what i'm saying more in depth.

Dont choose a speaker thats in the higher line of car audio or one that demands a whole lot of power to drive them. Some safe choices I can suggest are MB quart Discus or reference line components, Diamond Audio entry level components, or even Alpine Type S components. There are better components out there, but in order to get them to sound great, you'll need to have them amplified much more than the factory amp can supply.

Keep in mind, if you're looking for an increase in bass output, a sub setup will benifit you more. You wont likely get deeper sound output with just replacing the front door components. Just a heads up...