Not sure of ur budget, but the Berning inspired Linear Tube Audio might be your ticket.
As to reliability I think that thee late great Tim de Pavaracini said that power tubes have a great lifespan. I spoke to him and he said 300B's should be used in a push-pull configuration - never single ended - yes they can sound good but it kills those tubes. I just nodded along - frankly i have never understood amp topology properly save to say i know it from the blurb but can't build a circuit myself.