Ride the steel and carbon. If it feels like your own personal roller coaster (in a good way), go for it! Or, get the trusty old steed fit, ride it for a few months, and chances are it will act as a "gateway drug" to the steel and carbon--so I say, do both and save yourself some time. I still like riding my steel bike even though it's not quite the rush that my aluminum bike is. Who wants the same flavor of ice cream every day anyway?