I'm in my 9th season of triathlon and I've owned a tri bike for about 6 of those years.

I have to admit that I'm very pro carbon; I'm not sure it makes a speed difference, but they are just more sexy to me, and shouldn't your bike excite you?

Yes, wheels would be the first thing to upgrade; they don't need to be aero, but you can gain a lot when you trade out basic stock wheels for something nicer.

Riding in aero can get you some speed increase, but it *is* all about the engine. Don't assume that the new bike will get you 3.5mph.

Have you considered going used?