I recently bought a Gary Fisher Marlin which has been a great starter bike. . I live in GA, and luckily have a pretty good range of trails. I was hoping I could get advice from some veterans on recommended upgrades. The first and most essential upgrade I bought was a pair of biking shorts. Currently I'm looking to buy clip pedals and shoes. I would also like any suggestions on a comfortable hydration pack when riding hard through trails. I appreciate all the help...