My 2c worth:
Beg, borrow or steal a carbon bike then race it and the 'nag alternatively across identical courses. If there is a definite performance advantage to using the carbon, then fill your boots and buy one.
BUT, don't ever sell the 'nag! You will never look at the carbon thing on a sunny sunday morning and think, "I'm going to take that beauty out for a spin now", and you will never get the sense of pride and sheer joy that you get from just admiring the quality of that fine steel frame, let alone flying along your favourite roads on it.
If I were you, I'd buy I big fat heavy old tank of a bike to train on for next to nothing. An old touring bike springs to mind. Do all your winter miles on this then race the nuts of the 'nag come spring. This will put you at a distinct advantage as most folk I see "training"or on club runs these days are doing so unnecessarily on sub 20lb bikes.