speakers with a "smooth" impedance curve

I had started a thread asking about speakers that are well designed for tube amps (I am currently using a Ming Da MC 34AB with 8 EL34 power tubes 75 wt/ch ultralinear; 40 wt/ch Class A).
There has been a consistent recommendation for efficient speakers with a "smooth impedance curve".

Any recommendations out there for some tower speakers in the less than $5000 price range with smooth impedance curves that are "tube friendly"?