I don't see the necessary dichotomy of your good old bike with its 27" wheels versus the expensive carbon bike. There are many greades and price points in between, including seeking the best possible 27" wheel and seeing how it is when you make the best of it. Next stage would be to replace 27" with 700. Most brakes/frames should handle it without issue. And among 700, the price points will range from good used wheels needing your choice of tires, to the >$1k wheel set you'd get on the feared carbon bike.
The $700c conversion should be cash and carry at a good LBS - probably easier than 27" tire replacement.