I bought my first Mark IV in ~1990 I think... it was right when they came out. I had gone through the whole rack thing with a Studio Pre and then a Quad. The Mark IV was it for me... things seemed too easy after about 10 years and I strayed. I bought a Dual Recto, then a Soldano SLO. The Soldano is an amzaing amp, but it seemed to be lacking something. I had bought and sold a couple Mark IV's by this time and wanted to believe that the Soldano was the answer to my problems, but I didn't seem to be fully on board with the idea.
I just went back to my Mark IV earlier this week and now know why I loved this amp in the first place. It is, for me, the best tone one can get. I am running it through a Recto 2x12 and an older Mesa 1x15 with an EV (discontinued).