To get the best sound out of the Conrad or ARC make sure that the input impedance of the S/300 is at least 10x or 100x greater than the output impedance of the preamplifer. That is why Thorman thought that the ARC was bright and shrill and why the Classe sounded very sweet.
If build quality makes a difference the ARC is better.
If build quality makes a difference the ARC is better.