Dtanclim-my system is on Audiogon-it's Ayre Acoustics AX-7 & CX-7.
I would tend to suspect that your analysis is correct and the D15's would beat my speakers.
However the actual list price of the 150's in their day was only £150/200 less than what the D15's are now so rightly or wrongly I suspect the improvement might not be massive.