I remember reading an article many years ago (can't remember
where) addressing this very question. I don't recall the details either, but the conclusion was that Tube Pre and SS amp was the way to go. It had to do with the amount of tube sound ("distortion") each one added to the "tube sound". The author believed that a tube amp was too much of that sound.
Don't think I necessarily agree with his opinion, but it influenced me enough that when the time came, I went tube pre first and intended to stay SS amp and see how I liked it, but I still drool over the thought of some nice big tube mono blocks (

Gary and Hugh!).
I would guess it depends on how much of that magic tube sound you were after.
A little = Tube Pre and SS Amp
More = SS Pre and Tube Amp
Max = Tubes everywhere