The Gryphon pre amps have never been on par with their power amps . I am speaking especially of the Antellion pre-power combo . Having said that , it has been reported that the Pandora is a step in the right direction to balance out the previous mentioned shortfall . If your ARC is compatible with the Mephisto , theARC40 +Mephisto Solo would be the way to go, always nice to have a tube in the chain for that touch of magic . My preference is that the tube rather be in the pre than the power . Depending on how big your room is ,your listening levels are, I am quite certain that a Mephisto Stereo should be sufficient to bear ripe enough fruit , but the Solo it is if you do not want to die wondering
Good luck in your quest .