Money does not equal speed, unless you're going from 25-30 pound tank to a svelte 15-19 pound carbon racer. Before you spend a dime on one single new part or a new bike - make damn sure your BIKE FIT is correct and optimal to your body type and riding style. Optimize yourself first, optimize your equipment later. If your current carbon frame is a nice one - decent weight and stiffness, your first, best bang for the buck is a new wheel set. Carbon or Aluminum makes little difference, but the newer generation wider rims are highly recommended. A set of high quality aluminum rims are just as light as - and can be even more durable than carbon. I personally swear by Boyd Wheels and have two sets of their Altamonts.
If you want a new bike, decide what you want to spend and go for the best combination of geometry, components, and weight.
Never forget - it's a LOT easier to lose 5 lbs from a flabby butt than paying for ever lighter components to shave it off your bike.