Mimi- your fundamental problem is that you don't understand gearing. First of all, groups, like record, chorus, veloce, indicate component weight and performance. For example Record is for racing so is lighter and more expensive than chorus which is lighter and more expensive than veloce. On the shimano line, it goes durace>ultegra>105. To choose the gear range you want, go to Sheldon Brown's website and click on his gear caluclator (
http://www.sheldonbrown.com/gears/). While gear inches may not have too much meaning to you now, try viewing the results by speed. Input a typical cadence for you, and this will tell you how fast you'll go in a given cadence in a given gear. Then, pay attention to what gears you use on what terrain, to get a sense for the range you need. Turn those numbers into gear ratios so you can start thinking about it that way, since there are lots of different ways to get the same gear ratio.