If you have ridden RAGBRAI and are now interested in getting yourself a bike, I suspect you are or are at least becoming a pretty serious rider. The big question is do you want to do rides like RAGBRAI at a recreational pace or do you want to be up front. If you have a competitive nature and want to be up front, you need a very different bicycle than if you want to ride at a relaxed, recreational pace.
I strongly urge you to think this over then head out to your local bike shop and talk over your needs, expectations and budget. No doubt, they'll have Cannondale, Specialized, Trek, and perhaps Giant and some other brands to take a look at. These are all fine machines and will get you to your goal.
At your size, you are going to put a whipping on wheels. I'd particularly question shop people about the strength and longevity of the wheels you are buying. If they suggest you spend extra and buy a stronger set of wheels, I'd take the advice seriously.
Hope you love you new bike and I hope this helps.