Do you start fine tuning the system with cables or tubes ?

audphile1, you are right. I think, my system is fine tuned enough. Next step would probably be speakers upgrade. As for the source, well, Nottingham Spacedeck/Spacearm are quite good, separate tube phono stage perhaps to begin with.

@faustuss 

I’m being sarcastic here. I do love the sound of good tube gear. I don’t love tje maintenance though. My most recent tube component acquisition was a phono stage. I liked it a lot but I like my solid state phono as well and two weeks with tubes and tube rolling reminded me why I sold all my tube gear few years ago. I can’t deny the sound though. But properly designed modern solid state components don’t give anything up to modern solid state in my opinion 

@audphile1 

"I’m being sarcastic here. I do love the sound of good tube gear. I don’t love tje maintenance though. My most recent tube component acquisition was a phono stage. I liked it a lot but I like my solid state phono as well and two weeks with tubes and tube rolling reminded me why I sold all my tube gear few years ago. I can’t deny the sound though. But properly designed modern solid state components don’t give anything up to modern solid state in my opinion"

I've only ever had my equipment in every five years or so for the things that my technicians recommended. Cleaning and checking that everything is in spec, never recommended tube replacement. If you're having maintenance issues its probably all the micky-ing you're doing with the tube rolling and such. Left to what the designer intended they usually work fine for decades.

But how do you usually proceed ?

1st tubes, 2nd cables.

Learning the effects of tubes and cables usually requires hands on listening and subjective preferences. 

@faustuss depends on a component. Some run tubes harder and even the small signal tubes will wear out in 2 years. In process they gradually get worse. Power tubes only last about 1000-2000 hours. When they fail they can take out other parts and render the component useless. 
But yes typically with good components using the manufacturer recommended tubes might keep you out of trouble. I’m not anti tubes. I just know I’m done with tube gear for time being. And dumping money into tubes with today’s prices, you are more likely to get better ROI out of component upgrade.