$3500 Anthem MRX 1120:
$2200 Marantz SR-7011:
No, you will not hear the distortion at these low levels, but it seems fair to associate lower distortion with better circuit design and higher quality components/build quality.
The Anthem never gets below 0.003% distortion and climbs to ~0.0045 by 50Watts output.
The Marantz gets down around 0.002% and does not exceed 0.003% as it climbs to 50Watts output.
At 100Watts, the Anthem is at 0.008% distortion and the Marantz is at 0.0045%.
So through the main operational range, the Anthem has 50% (or greater) more distortion than the Marantz.
From the other posts, it seems that the Marantz has more features.
So, saving $1300 gets you better design & build quality and more features!