Seriously consider a JWN tube amp by Jim Nicholls. All his amps accept a variety of tubes and are all autobias even when changing tube types. They're extremely robust and all come with a liftime warranty on labor,and very reasonably priced. The only negative is the wait time which can be several months as this is a side business for Jim
jwnamplifiers.vpweb.com/
jwnamplifiers.vpweb.com/