Thanks for all the great replies. I really have a lot to think about. Our roads here are pretty rough--even the ones that are in good shape (and the majority aren't--lots of cracks and repaired potholes and even real potholes to negotiate). That's one of the main reasons I would consider carbon. I haven't really thought much about upgrading my current frame. That might be a good option for now--lighter wheels (I know I can get Mavic, not sure about other options), a new crankset to improve my front gearing. Could I get eight cogs on the back without spreading the frame?

As to testing bikes, I'll have to see what I can do. All the bike shops are in Santiago, which complicates things, and I'm not sure how much test riding they allow.