Ralph (Atma-Sphere) i got great sound with a Townshend Allegri+ with a pair of your mono's, one of the best sounds i have heard.The Townsend is a Transformer Volume Control rather than a simple passive (potentiometer)- a bit different in principle than what has been discussed here so far.
If the output of the source is direct coupled then passive controls have a better chance of working. This is one of the reasons you see so much variation in user experiences.