A system can only be as good as its weakest link. And for vinyl playback, the weak link would be sending the analog signals through the Marantz AVR's preamp. And I just don't mean its phono stage either but its preamp section. Even in so called "pure direct mode", its an afterthought. That phono input the AVR has is just a convenience and not for true hi fi performance.
So I disagree about a new TT/cartridge - it would all be wasted going through the AVR. Concentrate on the weak link and getting the AVR out of the analog signal chain. Find a nice stereo preamp with or without a phono stage because you can always add an external one. If the pre-amp has an HT bypass feature even better. This will allow your AVR to be integrated into your stereo system. If it doesn't, you can still integrate by determining the Unity Gain position on your stereo preamp. Google HT Bypass and Unity Gain to learn more.
An analog source is best kept with analog electronics.
So I disagree about a new TT/cartridge - it would all be wasted going through the AVR. Concentrate on the weak link and getting the AVR out of the analog signal chain. Find a nice stereo preamp with or without a phono stage because you can always add an external one. If the pre-amp has an HT bypass feature even better. This will allow your AVR to be integrated into your stereo system. If it doesn't, you can still integrate by determining the Unity Gain position on your stereo preamp. Google HT Bypass and Unity Gain to learn more.
An analog source is best kept with analog electronics.