Matt, checked the Solstice link. Those are nice speakers!
As far as the measurements go, are you planning to do any off axis measurements? Also, does your test software have a function to allow you to adjust for room acoustics? That might give you additional data. I do like the fact that you are making your measurements in a consistent manner.
What is interesting is 1) the big notches at 700 and 800 mHz from the Eminence (speaker bound?), 2) the fact that all three have approximately the same notch at 1K (amp bound?) and 3) the Vintage Purple has the flattest trace while the Eminence and WGS Retro have the pretty much the same trace at 10K and above (speaker bound again?). In any case, it's all interesting.
