Much obviously depends on the terrain you'll be in. If in hilly or mountainous you would be best served by a mountain triple front crank (at least 46-36-26)and a wide range rear cassette. Personally, I'd opt for an eight speed for the simple reason that an eight speed chain is stronger and cheaper than a ten speed (eight speed cassettes are cheaper too). Also, most touring bikes are set up with triples. Further, look on Sheldon Brown's website http://www.sheldonbrown.com/ for article on gear ratios to answer your questions.