I still have my GK MB800 as my back-up. Great little head, and so loud, but my MG800 requires much less knob twisting, and the notes have a little more "girth" to them.
I love the tone of the MB800, but I had two brand new go out in less than 6 months. So I'm not going to use GK anymore, not reliable in my experience. I have the new replacement head that I just received up for sale.

