Is a '06 Kona Fire Mountain a good deal for a beginner at $385?
A Kona Fire Mountain at this price point is great bike for a beginner especially if the alternatives are *mart bikes. You are not going to set the world on fire with the list of specs on this bike (Suntour fork, Shimano Acera, etc.)
But it is a disc frame and you can easily build on a frame like this. I have a Kona Blast that I have slowly been swapping parts out and really like the bike. You'll find that with Kona a lot of their XC bikes share the same frame. The only difference is the paint job, the name and the list of components.