If I upgrade stock speakers would the sound be improved?

 

Depending on RMS ratings, the aftermarket speakers may or may not get the recommended power. According to a post on here on a 2002 cl with Bose, the stock speakers are around 25 RMS @ 4 ohms. This might help a little bit for someone with extensive knowledge on the subject:

The CL has the following content

6.5" woofer front doors (2 ohm)

2" twiddler front door (4 ohm)

6x9 speaker rear (2 ohm)