Your Marantz is a receiver having a tuner, phonostage (sometimes called a phono preamp), a linestage preamp and an amplifier. There are integrated amplifiers having a line stage preamp and an amplifier combined. Some also include an internal phonostage. Many prefer a linestage integrated with a separate phonostage for cartridge matching flexibility and sound quality, however this is more true at a budget higher than that under discussion here.
In your specific case I would recommend the purchase of an integrated amplifier or receiver which includes internal phonostage. Check out the A-Sxxx series as one example.
In your specific case I would recommend the purchase of an integrated amplifier or receiver which includes internal phonostage. Check out the A-Sxxx series as one example.