Fit is very individual, as is preference for materials. If you don't think you need a full carbon bike, then there is no reason to get one! They are expensive and fragile, in my opinion.
Steel is quite nice to ride, too, especially with a carbon fork. It might be something you wish to consider. Jamis makes some really nice steel bikes. I prefer steel/carbon to aluminum. Aluminum bikes, for me, are rough and uncomfortable.
Your body proportions will largely determine fit, too. For instance, I'm 5'-6" and I ride a 49cm road bike. Most people would say that's too small for me, but it's the most comfortable bike I've ridden, ever, and I've ridden alot of bikes.
So pay attention to fit, including (or especially) the top tube length. Keep riding bikes and you will find one that calls out to you. Good luck.