What is most important part of a system?

czarivey
you are the most important part of system.

ordinarily I'd agree with you but I prefer to restate your comment as,

you are the most important problem with the system.

Fair enough?

The most important part of any audio system is the person listening to it, and their confirmation bias affected brain.  Also, what they are drinking...

Note:  the OP does not know if the CD and LP were mastered the same...

I have been saying the source for many years.  I get the other posts also but if you are using a cheap $19 Walmart CDP and you think that will get you the best sound out of your $100K amps, $100K Preamp, $100K Speakers, Your $100K dedicated lines and line conditioners, Room treatments, etc. then who am I to argue?

Happy Listening.

One thing for sure.I sold audio for years. By far the most distortion is your loudspeakers. Even 1-2% is far more than any other piece of equipmrnt.That is where probably more money should be spent to get the highest quality.  Your sourse for sure is the most critical for precision 
Of the event.  Everything starts from the sourse and detail once lost 
Cannot be made up else where that is why  you should get the best turntable 
Including Arm  and cartridge and sound Different this includes Digital .Makes sure it's sonic signature is a good fit before pulling the trigger.

IMO, the pre-amp is the heart of any system. Some will view this as the most important.  After the pre-amp, Speakers are on-deck.

Happy Listening!