Once again Ralph makes a good point. I have Zu speakers that love tubes. They are fast and immediate for sure, and run tubes all the way through. BAT-Zesto-Mac MC 60s and believe it or not there isn't a euphonic excess to be had. So IMO the speakers determine how much tubiness will come through to a large extent.
Phono/preamp/amp chain. One of them tube the others SS. Which one?
Perhaps any one would do if done right. What would be your preference, generally speaking? Let's assume MC cartridge. This move could be permanent or could be the first step on the way to full tube system. I would probably choose the phono.