'01 Camry sounds similar to my '03 Tacoma.
The 4 speakers in the doors are actually function as two speakers, one in each door. The tweeter and midbass are separate, but function as a single speaker.
One 4-channel amplifier is sufficient for that setup.
Usually, a stock system only includes an amplifier for the 'premium' sound system. You can find out if that is the case by having a dealer decode your VIN.