Yamaha A-S1200 + KEF R3 Meta + KEF KC62 — Good Match?

Yes, the A - S1200 is a fine match. For the $3K+ you spent it better be! 

All amps of low noise, distortion and low output impedance will sound indistinguishable.

A Fosi V3 would suffice and save you a lot of money, though lacking the bragging rights of the A - S1200.

From the specs it looks good. I have owned a couple pairs of KEF speakers, which can be hard to drive, and the Yamaha should be able to handle them well. It will come down to whether you like the combination. Forewarning, if it is brand new, don’t jump to conclusions when you first hear it, give it a couple weeks of continuous play as it will take time to break in.

A vast majority of Audiophiles do NOT buy equipment for bragging rights. The few that still believe this outdated stereotype are usually DIY, vintage only, naysayers, a miser or just an overall negative unhappy person! Regarding the OP’s question, I would try an amplifier with more warmth/density and overall darker presentation. McIntosh, Electrocompaniet, Audia Flight, Norma Audio or even a less refined Hegel might prove a better match with KEF.