02 GMC Sierra Factory Speaker Replacement

I am looking to replace the factory speakers in my 02 GMC Sierra Ext. Cab. I want to maintain the stock look. I am not looking to do anything drastic, just to improve the sound quality. I have a Pioneer 3600 (4x50W) head unit installed. Currently the front doors have 2 speakers each in a single enclosure. The rear doors each have a single 5 1/4 speaker wheich can barely be heard. A local dealer has suggested that I eliminate the smaller speakers on the front door and install a single Rockford Fossgate in each door. The Rockfords have the built in tweeter. They also suggested replacing the rear factory speakers with a similar Rockford.

Will this improve the sound in my truck? Is going from 2 speakers to one, in the front, the right thing to do?

Any opinions would be appreciated.