Find a good local bike shop, and they'll be able to give you a bunch of great advice on materials and fitment.
I just purchased a Cannondale Caad 8, size 63 cm (I was told they don't come any larger, unless custom made!); and a Specialized Dolce for my wife. Both aluminum, the caad8 is hand welded, a bit lighter than the girl bike (though it's much larger). The fork and seat post are carbon, and the dolce also has carbon seat stays, so there's flex where you need it (smoother ride).
The shop was awesome, the owner is an expert in bike fitting. They bike purchase includes any fitting, including replacing parts (like the tube that goes from the stem to the handlebars, not sure what it's called).
I could imagine that if I bought online or from another individual, I'd be unhappy with the bike because it wouldn't feel right without the proper fitting. If you do buy that way, definitely get it adjusted by someone who knows what they're doing.
I did blow a bunch of dough (around $2,600), but I was happy with what we got.