Normally one would expect the cartridge to be the most important. After all it is a transducer - the others being microphones and loudspeakers.
However it is the turntable that is the most important. First, there are speed issues. This is expensive to get right. The cost effective way is to get a Direct Drive. Second is vibrations. This is critical because the signal from a cartridge is magnified some 10,000 times form cartridge to loudspeaker. So the smallest imperfections are audible. Vibrations come from ambient vibrations in the room (typically from outside the room), footfall, the cartridge itself colliding with the vinyl wall (and often magnified by the platter), the sound from the speakers themselves hitting the turntable, the bearing. All these issues can be resolved but not easily.
Compare this to a tonearm. They have their issues but the difference between an average tonearm and a top one is not as much as any other Analogue component, even including phono stages. I bought a very high end tonearm from Origin Live, but with a few months I sold it and went back to my Jelco.
My ranking from most to least:
Turntable;
Cartridge;
Phono Stage;
Tonearm.
However it is the turntable that is the most important. First, there are speed issues. This is expensive to get right. The cost effective way is to get a Direct Drive. Second is vibrations. This is critical because the signal from a cartridge is magnified some 10,000 times form cartridge to loudspeaker. So the smallest imperfections are audible. Vibrations come from ambient vibrations in the room (typically from outside the room), footfall, the cartridge itself colliding with the vinyl wall (and often magnified by the platter), the sound from the speakers themselves hitting the turntable, the bearing. All these issues can be resolved but not easily.
Compare this to a tonearm. They have their issues but the difference between an average tonearm and a top one is not as much as any other Analogue component, even including phono stages. I bought a very high end tonearm from Origin Live, but with a few months I sold it and went back to my Jelco.
My ranking from most to least:
Turntable;
Cartridge;
Phono Stage;
Tonearm.