If you don't mind I'm going to question the logic. How do you plan on breaking into a market heavily saturated with established competitors? True, there may be external economies of scale in the radio industry that reduce costs, but that doesn't necessarily help your station vis-a-vis others that people already know and love, which interestingly enough brings me to my point. Expanding into other genres from the outset would immediately help delineate your product from the legions of heavy metal/hard rock stations out there. Sure, it doesn't necessarily have to be over 50% of the material you play, but setting aside maybe 10% of airtime for other genres might be a good way of getting some recognition.
There's a substantial amount of beloved death metal from the 90's - doom and prog were also expanding then. It's a good thing that you plan on playing some power metal, that's a genre that doesn't get a lot of play outside of Judas Priest and Iron Maiden. However, I think it would help things if you further establish your radio station as being open to all classic metal and not just the material most folks have already heard.