I used to own a SA100 MKIII. It is supposed to have very similar sound to the SA250 MKIII. It is a class A design, runs very warm and has the most liquid midrange of any SS amp I have owned. It also has beautiful tone, is a bit warm sounding with excellent bass but not especially open (when running my Maggie 1.6s), I now own a 300B SET and the Plinius is the closest to the SET sound I ever heard from SS.