I am currently looking at the 150a Reference as well. How does it compare with the other "usual suspects" in the price range (Plinius SA100 MKIII, McCormack DNA-125/225, Pass X-150 ect?)
I had a set of Sixpacs: they are great if you are looking for a tube sound. Exceptionally refined and smooth, seemed more or less tonally accurate. But, in my system, I preferred SS.