Easy to drive, outstandingly natural sound from 40-50 Hz up.....AN-E, O/96, others?

Thanks Al, I knew I left one off my short list.

After hearing the bass improvement in my room after moving from large speakers to somewhat smaller speakers with two subs, I will probably continue down that path.  The trick is finding smaller speakers that provide the desired level of dynamics, scale, and rich tonality within their frequency range. The "smaller" stand-mounted speakers I currently use have two 9-inch woofers and weigh over 100 lbs each and they more than meet my dynamics, scale, and tone requirements.  They also use sealed boxes, which I find to improve bass.

This is a bit of a conundrum since my current set up sounds very good and standing pat is probably a good option, but moving to more efficient speakers and lower powered amplification aligns with my "simplification" goals. I know which amplifier I would like to try but all of this gets expensive and tiring since I would then have to sell and relocate 350 pounds of speakers and stands.  I am however interested to hear about which speakers are available that would be well driven by 50/100 wpc into 8/4 ohms.

@salectric , I have been interested in Spendor SP 100s, as well as Harbeth M40.2s but both of those have relatively low sensitivity for a 50-watt amp, although both are somewhat "easy" to drive from the standpoint of impedance.  Just not sure 50 watts would make them jump.

From Stereophile:

Spendor Classic SP100R2 loudspeaker Specifications
Sensitivity: 89dB/W/m. Impedance: 8 ohms nominal, 5.5 ohms minimum.

Harbeth M40.1 loudspeaker Specifications
Sensitivity: 85dB/W/m. Impedance: 6 ohms nominal. Suggested amplification: >50W.

A wide variety of interesting options.
Thank you everyone.

@jond 
Your questions raise some good points and even though the thought of simplifying my system is attractive, the simplest route is probably to stick with the speakers and amps that I already own.  I do have a 50-watt amp in mind but for the power I need to drive my current speakers, it just isn't in the cards.

There are some very interesting speaker choices provided in this thread so I expect others will benefit from the responses here.  I wish I had posted this 20 years ago when I started down this audio road.  Using more efficient speakers would have opened up a much larger variety of amplification choices, virtually all of which would have been less expensive than the amps I need to drive my inefficient speakers.

I am curious about any downsides of some of the efficient speakers mentioned here, such as the Klipsch Heresys or AN-Es, like midrange colorations or other sonic aberrations.  I have a friend who has been using the Heresys for years and likes them.

@exlibris 
Where did you find a good-sounding high pass filter made with high quality components, or did you make one yourself.
I have looked at Vandersteen's M7-HP, which is made for their Model 7 series speakers and appears to be well-constructed, but it costs $2K/pair and rolls off from 100 Hz, which is higher than I want.
https://www.vandersteen.com/categories/crossovers

I agree with your thoughts on the AN Duke.  Another option might be to use a high-pass filter like Vandersteen uses, and then roll the subs up to match the rolled off frequency and output of the main AN speakers.  Of course you may accomplish the same thing more simply by moving them out from the wall but the high pass would (theoretically) reduce the work required by the main amplifier.

BTW, I would like to hear your swarm system some day.  Adding a second Aerial sub was a huge benefit to the sound of my system, in particular by better controlling bass in my room. 

@mrdecibel 

A good set of horns will excite and delight.

How about Klipschorns?  How good are they? Can they be set up or modified (if necessary) to avoid thinness, honkyness, or other horn-related aberrations?  Can I get the exciting dynamics and a rich tonality from an easy to drive horn speaker?

@mrdecibel 
I could do corners, or not, so either Klipschorn or LaScala are possible, and the room is big enough.  What do you mean by;

"when I get done with a pair, none of the nasties are present"

Are you talking about making modifications you have learned over the years, or do you have a business to modify/improve Klipsch Heritage speakers?  Pardon please if I have missed something earlier.

too strong?  Nah, just too busy here.
I wish I would have tried this stuff years ago.  It is tough to switch directions now that I have my speaker system pretty well dialed in for great sound, but they are inefficient and need lots of power to sound their best.  
There is a 50 watt amp I would like to try but it wouldn't stand a chance with my speakers.  The amps I have are 90+ percent of the way to nirvana but just falling short in one area.  Since I already own the speakers, trying different amps until I find something better may still be the easiest direction for me.  Problem is, I have tried several pretty good amps and the amps I own now are better than all of the others I have tried, and I don't want to spend a fortune trying high powered amps.  One recent change I made is to try going DAC-direct, first with the Metrum Jade I recently purchased for a second system and then just this week with Metrum's flagship Adagio I purchased after hearing the Jade.  The Adagio has been warming up for a couple of days and I will get to listen to my system without my preamp this weekend.

I was hoping to see some recommendations in this thread for relatively high sensitivity speakers (like 95dB +) that can be driven hard with 50 wpc and that display tonal density, strong dynamics, and a natural sound without added edginess, shrillness, honking, or other issues sometimes reported with horns and other really high efficiency speakers.  I think there are a few of those types of speakers mentioned here that would be worth hearing, but I am not convinced Klipsch speakers meet all of those goals....although there is an interesting pair of Belle Klipsch speakers that were recently listed for sale.  I need to go to show where I can hear some different high efficiency speakers.