A method for rendering media content by a first playback device, the method comprising: while an amplifier in the first playback device is in an inactive state, detecting, by a proximity sensor on the first playback device, movement in relation to the first playback device, wherein, in the inactive state, the amplifier is in a lower-power mode or a powered off mode and media content cannot be rendered by the first playback device until the amplifier is activated, and wherein, in the inactive state, a communication interface of the first playback device remains active while the amplifier is inactive; and responsive to the detected movement: causing, by the first playback device, the amplifier to enter an active state such that the amplifier is configured to produce amplified audio signals in response to a user input to cause the first playback device to render media content; sending, from the first playback device to a second playback device (1002, 1004, 1006), an activation message that causes an amplifier of the second playback device (1002, 1004, 1006) to enter the active state, wherein the first playback device determines that the amplifier of the second playback device (1002, 1004, 1006) is in an inactive state before sending the activation message to the second playback device (1002, 1004, 1006); retrieving media content from a networked audio source; storing the retrieved media content on a data storage medium of the first playback device to pre-cache the retrieved media content; receiving, by the first playback device while the amplifier is in the active state, a user input to cause the first playback device to render media content; and responsive to the user input, causing the first playback device to render media content in synchrony with the second playback device (1002, 1004, 1006), wherein causing the first playback device to render media content comprises causing the first playback device to render the pre-cached media content. while an amplifier in the first playback device is in an inactive state, detecting, by a proximity sensor on the first playback device, movement in relation to the first playback device, wherein, in the inactive state, the amplifier is in a lower-power mode or a powered off mode and media content cannot be rendered by the first playback device until the amplifier is activated, and wherein, in the inactive state, a communication interface of the first playback device remains active while the amplifier is inactive; and responsive to the detected movement: causing, by the first playback device, the amplifier to enter an active state such that the amplifier is configured to produce amplified audio signals in response to a user input to cause the first playback device to render media content; sending, from the first playback device to a second playback device (1002, 1004, 1006), an activation message that causes an amplifier of the second playback device (1002, 1004, 1006) to enter the active state, wherein the first playback device determines that the amplifier of the second playback device (1002, 1004, 1006) is in an inactive state before sending the activation message to the second playback device (1002, 1004, 1006); retrieving media content from a networked audio source; storing the retrieved media content on a data storage medium of the first playback device to pre-cache the retrieved media content; receiving, by the first playback device while the amplifier is in the active state, a user input to cause the first playback device to render media content; and responsive to the user input, causing the first playback device to render media content in synchrony with the second playback device (1002, 1004, 1006), wherein causing the first playback device to render media content comprises causing the first playback device to render the pre-cached media content. causing, by the first playback device, the amplifier to enter an active state such that the amplifier is configured to produce amplified audio signals in response to a user input to cause the first playback device to render media content; sending, from the first playback device to a second playback device (1002, 1004, 1006), an activation message that causes an amplifier of the second playback device (1002, 1004, 1006) to enter the active state, wherein the first playback device determines that the amplifier of the second playback device (1002, 1004, 1006) is in an inactive state before sending the activation message to the second playback device (1002, 1004, 1006); retrieving media content from a networked audio source; storing the retrieved media content on a data storage medium of the first playback device to pre-cache the retrieved media content; receiving, by the first playback device while the amplifier is in the active state, a user input to cause the first playback device to render media content; and responsive to the user input, causing the first playback device to render media content in synchrony with the second playback device (1002, 1004, 1006), wherein causing the first playback device to render media content comprises causing the first playback device to render the pre-cached media content.