Pardon me Jay, I neglected to mention that phase characteristics in the speaker also influence amp performance. Phase lead and lag illustrate reactive characteristics of the load, which are far more difficult for an amp to drive than a purely resistive load. Thiel speakers do a good job of presenting a non-reactive resistive load which allows the amp its best shot of capably driving that load. So, even though Thiel impedance is very low, requiring lots of current, at least the load is fairly benign.