introducing tube eq. into ss system

If you were going to introduce 1 piece of tube equipment into an ss system which piece would you start with. digital source, amp, pre amp. Just curious.
I believe if you like tubes the biggest sonic change would be a tube amp. I just put in a tube amp with real good ss and digital front. For me it's perfect.
My preference is a tube preamp with a solid state amp. A previous system I had with this arrangement had the sweetness of tubes and the power of solid state. Sound great.
closer to the source the better the tube effect IMHO
tube buffer between the cd and pre amp, or tubed pre amp.
I had a hybrid tube preamp (Melos Sha-1) with MOSFET output and when I gave the Channel Islands passive a tryout it wasn't funny. The same happened when I brought it over to someone here who's got a $3500 tube preamp. My experience tells me that a hybrid tube amp (like the Van Alstine) would be a good choice--or a well designed tube amp. Unless your IC runs are long I'd stick to the passive pre/tube power amp combo.

Disclaimer: my system is 100% solid state...and will stay solid state.