What data are you using? People assume that because of how much power they will handle. I have JBLs with 96db rating--by JBL, and they can handle 250 watts per channel. They will run fine on far less than that--though I don't because I don't have to.
I have no idea what you are talking about. Anyone who tries to determine sensitivity based on power handling capability is being silly.
You can run just about any speakers with just about any amp. No news there. From a power standpoint, it comes down to whether or not the amp can deliver desired loudness without significant clipping. I explained that already, above, in an earlier post.
However, I do have a lot of experience with the classic AR speakers, having owned just about all of them and having done extensive restoration and repair work on at least another 30 pairs of them.
I've also developed good relationships with several AR experts, including one who worked at the Cambridge facility for many years. These gentlemen and others at the CSP site have worked long and hard to keep the AR legacy alive, to preserve the company's history, and to develop restoration strategies to best retain the original sound qualities of these wonderful old speakers.
You can certainly use Google to find threads in which some of these experts are quite clear about the sensitivity of the classic series as all being in the 85-88dB range, which is in keeping with my own findings in comparing their output to my Vandersteens, which are rated at 86dB.
Additionally, if you dig deep enough, you will find some sensitivity measurements done a few years ago by an AR enthusiast whose name I don't recall. Perhaps someone else here can point you to his data.
Finally, here is a link to a chart of AR performance data compiled, I believe, by AK member rxdx.
http://www.aphenos.net/electronics/speakers/klh/all_ar.htm
Bottom line, the OP can certainly use his little amp to good result with any of the classic AR speakers, assuming he has no desire to listen at higher levels than I described earlier. Heck, he can use a 5 watt amp with no problems...again, assuming it can drive the speakers loud enough to satisfy him while maintaining at least 9dB in reserve to minimize clipping of transients.
But to my original point...you touted AR speakers as being "super high efficiency". This is not the case, nor is it even close to being the case.