I see a lot of support for the 105 components, but I found that if you can find a bike with at least an Ultegra deraileur, you'll be happier in the long run. I had 105 components on my last bike & was not thrilled with the performance.
I'd say consider looking for a road frame over a tri frame at this stage. Specialized, Giant & Trek all make nice bikes for the money you're looking to spend.
Once you start getting "upgradeitis," it's probably time to start saving for your second bike.
