It has been exciting and fun to watch the "counter current" trend in the increasing availability of all-tube (or at least "mostly tube") bass heads, in light of the movement towards lighter-weight, more compact heads. Both products have their place, for sure, and it's great to be able to have it both ways!
The OP's choice of Orange, Fender and Mesa/Boogie are certainly all great choices (though I have not heard the new Mesa/Boogie heads yet). We did recently
Link Removed, and it proved to be very impressive. I have an Orange AD200, and while it isn't the most tonally flexible head out there, if you like what it does, it does that very well. Of course, the SVT is always a viable option as well, and a killer one, at that. Though I haven't heard the newer Boogie heads, I absolutely love my older Bass 400 and D-180, so I have high hopes.
Some of the other suggestions in this thread are also very good and worth considering. We
reviewed the Reeves C225 back in Bass Gear Magazine issue #2, and it remains one of my favorite all-tube heads. Traynor is another good choice.