I agree that the McCormack is the week link if looking for a tube sound, I also agree that the pre's mentioned are all nice sounding tubes and that the DNA.05 is a fine sounding amp, BUT, if you are truly trying to add a tube flavor to your system, no preamp will add near the flavor of a good tubed amp. So be prepared that if you take a preamp suggestion, it might or might not be "enough" of that tube flavor that you are looking for.
Tim
Tim