As others have noted, it could be the anthem has lower gain. It could also be an issue of the type of profile for the volume control (linear vs. logarithmic).
With regular potentiometers, it is actually preferrable to be working toward the higher range (less attenuation) because the two channels of the pot tend to track better. With stepped attenuators, this is less of an issue, and often the steps are wider near the top and bottom of the range, which makes it harder to find an ideal position.
As long as you can get your system as loud as you want with the Anthem, I don't see any real problem with having to operate the volume control at the higher end; this may actually be an advantage.
With regular potentiometers, it is actually preferrable to be working toward the higher range (less attenuation) because the two channels of the pot tend to track better. With stepped attenuators, this is less of an issue, and often the steps are wider near the top and bottom of the range, which makes it harder to find an ideal position.
As long as you can get your system as loud as you want with the Anthem, I don't see any real problem with having to operate the volume control at the higher end; this may actually be an advantage.