I'd buy an Aluminum frame with 105 components, and then invest in a power meter- probably a Quarq. You'll make more gains with proper training than you will with a few hundred grams off your gear.

Edit: if I were you, I'd first shell out some cash to get a good bike fit. I mean a really good fit. Then I'd base my decision on those numbers after chatting about it with the fitter. That will mean so much more in terms of comfort (not to mention power) than a carbon frame.