I'm just trying to get into riding and have decided that I would like to get one of the Cannondale CAADX bikes. I was told by a few people that I shouldn't even mess around with the Sora or Tiagra and should just go straight for the 105. I am extremely new to cycling but would like to get a bike that I won't outgrow quickly. I'd like it to last a number of years. I will mainly be doing road riding but would like the option to go offroad and try some cyclocross tracks. I have asked the question "what is the big difference between the three" and all I get as an answer is 'quality.' I realize the 105 is a better group than the other two and I'm willing to pay the extra money if it is worth it but what really makes it so much better? Is it faster? faster/smoother shifting? Less problems? I'd really like to know what I'm getting if I end up spending that kind of money. Maybe I am over purchasing for what I want, which I have a bad/good habit of. Buyers remorse is one of the worst feelings in the world in my opinion lol. But I also don't want to spend the extra few hundred if it will be a waste. Opinions? Tech facts? I'm open to any criticism or helpful advice! Thanks everyone!