Wow, killer bike and deal. As a reference I just easily sold a Hardrock Sport of the same era in similar condition for $150, and that's a good many steps below the Rockhopper in terms of performance. Looks like you have a good build planned too, I'm eager to see how this one turns out. Keep us posted.
The Specialized mountain bikes from that era were really great rides, despite the somewhat stretched out frame dimensions. The Hardrock Sport I had was surprisingly nimble. The Suntour drivetrain seriously sucked, though.