Responding to the Original Post, I have a Markbass Tube 800 head and really like it. I can get a satisfying tube tone from it, and its part of the rig I use when I play rock gigs. The moment I bought it I turned to "tube engage" knob to 11 and have kept it there since.
But I also have an several vintage Ampeg tune amps: a B-15N from 1974, a B-18 from 1966 and a B25B from 1969. While the Markbass is a great amp that has so many advantages over my vintage ones, it ain't no tube amp. I use it in place of a tube amp because I like its tube sound, is very light and highly dependable.