The Rockhopper is a great bike that will serve you well for a long time. However, before you commit to this bike (or any bike for that matter), you should see if the bike feels right to you.
If you want to stay closer to your budget then look at the base Rockhopper (if you can find one) or the Specialized Hard Rock model that is closer in price to what you're looking for. I like the Konas and I think in your price point you'll find the Kona Blast to be a pretty good bike. Gary Fischer also makes bikes that you may like.
The key is to try the bikes and see if they feel right to you. If you feel you're stretching beyond your budget, don't worry because at $500 you'll get a pretty decent entry-level bike that will suit your needs fine.