Those bikes seem a little on the expensive side for used touring bikes.
When you plan to spend a lot of time in the saddle over several days, I'd go with fit being the most important aspect.
For my money, if you can find a Surly dealer in your vicinity, go get yourself a Long Haul Trucker. It is about the price of the Cannondale (but without the accessories). If you're touring much, you'll be needing a GPS unit, so the computer becomes less important. Anyway, you can get one for about $30. The panniers and rack are more expensive, but you could maybe get away with a saddlebag to start off with, and build up as your needs change.
Of course, if you know the bike size for you already, you could always buy the LHT online. Cheaper.
Just my two cents.