Nobody got caught, you heard what you heard, I cited Placebo as a possibility only, not as fact. The only thing I was sure about was that the few extra watts of superiority of the 3040 could not have been the cause for the perceived difference, presumably better, sound quality.
The 2040 was rated 140W, 8 ohm at 0.06% vs the 3040's 150W. S&V bench tested the 2040, with two channels driving 8-ohm loads, reaches 0.1% distortion at 169.7 watts and 1% distortion at 195.9 watts. Into 4 ohms, the left channel reaches 0.1% distortion at 259.8 watts and 1% distortion at 317.1 watts.
That's actually better than the 150W rated 3060, also tested by S&V, with two channels driving 8-ohm loads, reaches 0.1% distortion at 159.0 watts and 1% distortion at 186.4 watts. Into 4 ohms, the amplifier reaches 0.1% distortion at 228.7 watts and 1% distortion at 294.3 watts.
The RX-A2040 has more than enough "clean" power for the LS50 that are mainly designed for near field enjoyment in smaller rooms and are suitable for people who enjoy their music loud. Given their impedance and phase angle graphs, I do believe they need good quality amps that are rated for 100 WPC into 4 ohms, if they are to be used to near their limits.
By the way, you mentioned Focal, I have a pair of Focal too, the 1028 Be. How would you compare your Focal with the KEF?