Steel is real, my friend, steel is real
I had an aluminum bike, then went for a steel Colnago Master XLight. Just loved that bike....then it rusted. My eyes still mist and my throat chokes up thinking about it (because it was my fault for not taking care of it better).
My replacement was a Surly Crosscheck, decked out as a fixie for commuting (mostly flat bike paths). Now I have a Gunnar - hand-made, custom fit, lower quality steel than some higher-end bikes but for someone my size and fitness level, saving 1-2kg on weight isn't going to make a difference. ( In my opinion, getting top of the line isn't that important - its easier & cheaper to cut kg from your body than from your bike! ) And as far as technology, it trickles down very fast - Ultegra of today is DuraAce from 2-3 years ago. For wheels, I go with beefier to handle potholes, not aero (tho modern aero wheels can handle rough roads, just watch Paris-Robaix (sp?), with over a dozen cobbled sectors.
To summarize, agree with Westwoody - get a bike fit, stick with the Tarmac till you can articulate what you like & don't like, save up $$ for the best you can buy but don't worry if that ends up being a slightly heavier bike or lower groupset - it'll just make you feel that much more manly when you drop dudes in the higher-end bikes going up hills or in the sprint!!