I recently upgraded from a 56/12 high gear, which was shifting fine for the past 10 years, to a 60/11 setup, and now I'm having problems. The FD was working fine but the bike shop replaced it anyway. Now it takes 4 rotations to jump from my 48 middle ring to the 60 big ring.

I may need to seek out a dérailleur expert, or build my own electronic one with a small stepper motor and actuator.

As for "making a difference," your 46/12 can hit 28 MPH @ 90 RPMs while a 52/12 can reach 32 MPH at the same cadence (calculated with 700 mm tires).