Per everyone else, there is not a whole lot worth proactively replacing. I bought a 105-mix bike in March and have ridden it about 2,200 miles so far. The 105 stuff is probably good for a season of solid training before it starts showing wear shift quality degrades. And, my crankset is a dirt cheap FSA Omega with a fair amount of lateral flex. I think your Gossamer is a great deal better.
Probably, your biggest aero improvement is the base bar. It is just a round tube.
Probably, your biggest aero improvement is the base bar. It is just a round tube.