So where should the tubes be?

Modifying an old Conrad-Johnson slogan: "Tubes Just Sound Right."

Tube - lets you listen to music.Solids - focuses attention or the greatness or failings of the gear.
Use tubes throughout, but keep the chain as short as possible. ;

I've 21 tubes in a record player only system. Can't get enough of 'em.

@millercarbon

Tubes should only be used where you want it to sound like music.

Would you kindly elaborate?

Wouldn’t one generally want it to all sound musical (unless perhaps for pro audio mixing)? 

Tube "sound" is all about the design and engineering of the electronics.  I have heard very neutral tube equipment, not warm, lush or thick.  Don't have that "tube sound" or "solid state sound."  Just music.  

Tubes belong wherever they sound right to the owner.