mbl 101 E versus Von Schweikert VR-7 SE

These are clearly fabulous speakers but has anyone auditioned both and made any real comparisons. I listen primarily to female vocals, Jazz and Classical music on CD/SACD
I can't comment upon the comparative sound quality, never having heard the VS's, but I do note that the mbl is unusually inefficient (and far less efficient than the very efficient VS), greatly limiting your choice of amplifiers.
What amps will you be using to drive the speakers?