Most power amps have an input sensitivity that a normal CD player's output of 2Vrms will either drive it to full output or overdrive it to distortion. Depends on the amp. In this case no gain, only attenuation is needed.
A phonostage will need alot of gain on the order of 40dB or more to get to a level getting close to a CD player. This depends on the phono cartridge output. In this case it depends on the phonostage gain whether more gain is needed after that stage to drive a power amp.