What size door speakers are in a 2005 chevy silverado?

The standard front speakers in a 2005 Chevy Silverado are 6-¾ in the front doors with tweeters mounted in the A pillars. The rear speakers can vary based on what sound package You have but are usually 6-½ or 6-¾. The most common upgrade done to the sound system in this truck is a set of two way components in the front doors, using both the factory woofer and tweeter locations to mount them. The rears are usually replaced with a set of 6-½ coax speakers, which have the woofer and tweeter as a single unit. These would also use the factory mounting locations. As long as You go with a mid tier or leSSReplacement there should be no reason to upgrade the in-dash unit or add an aftermarket amp unless You want to.