Are you saying your local shop is selling a silvertip for $600US? Is it used?

I think that might be fair depending on its condition, my silvertip cost $770US new 2 years ago.

The site you linked to was talking about a very different bike, on a midtown mini frame like the Silvertip you could deffinitly put a tripple crank on it. One advantage of the silvertip is that you can upgrade it with almost any normal bike parts.