@t_ramey
currently. OHM Walsh 5000's...
Also have had DynAudio Contour 60's, Klipsch Epic CF-4's hooked up for long test runs. For kicks I had some old OHM Pro-200's hooked up (sounded suprisingly good).
At a friends house I've heard Salk SS12's hooked up to the XP12 and X 150.8