It's been said before: spending money on a bike to go faster pales in comparison to strengthening the engine, up until you are close or really into the professional competitive level.
Put another way (IMHO), any decent road bike from the 70's onward, with your choice of period or modern component upgrades, will put you in the running with your peers (in terms of age and fitness). And if you're trying to compete in a group that is younger and/or stronger than yourself, I doubt upgrading your equipment to the latest and greatest is going to close the gap.