Think I want a tube system?

I've haven't listened to a tube system in 30 or 40 years. (I'm retired). I have several general questions. I hope y'all (South Alabama) will help me. I have a fair solid state power amp (Onkya M-504 165w per channel) No pre amp.
Which is the most important a tube pre amp or a tube power amp or both tubes. I would like to keep the power amp, but would sell if necessary. My second question is a little more complicated. If I play music from cds or internet download, isn't that digital. If I recall,digital is not an analog wave form but samples taken along it's path to reproduce an analog wave. The more samples the closer to analog. However, many people felt that no mater how many samples were taken, the nuance of a pure sound wave would be lost. If this is the case, what can tubes give me if my source is digital. Back to vinyl? Even then do they now record digital? I hope this is wrong.