I've decided to buy my first bike. I plan to be riding on plenty of trails as well as pavement. I went shopping around and the three bikes the places tried to sell me were the cannondale F7, cannondale F6, and the trek 4500. I know that each place is very biased and wants to get my sale. So I was wondering if anyone has any recommendations as to which one I would like best or if there are any other bikes I should look at. My price range is anywhere up to $500. I dont want a puny bike either. I hope it to last me a while as I get better. Thanks!