[Wind Chaser]

Along those lines, a lower mass also responds quicker.  I find my speakers with low-mass pure ribbon tweeters have more resolution at lower volumes than my speakers with dome tweeters.

Very true.  I have not heard a dome at any price that has the resolution of a ribbon.

[Quiet Earth]

I wasn't putting electrostats down, honest.  I was just saying that after living with them for 15 years I was able to move onward and upward. At the time, I also knew that no cone and dome speaker could ever do what my electrostat could. Then I heard an amp and two way box speaker that sounded a lot better than my full range electrostats. How could this be? All of my rules were being violated. That was about the time in my life I started to listen to results first, and subscribe to theories second. Again, I'm not saying electrostats aren't the best, I just found somethin' else that works better for me.

 For the record, single driver isn't really my bag either, although I do admire the potential. It seems like there are just as many problems as solutions with single drivers. Getting rid of the crossover is no guarantee to a beautiful and coherent sound. I prefer a two way speaker and I like listening at low to reasonable volume levels. Like I said earlier, 85dB is getting loud for me. I didn't ditch electrostats 'cause I'm a headbanger, so I doubt if I"m that much in the minority.

This has been an interesting thread, academic as it may be. Lots of roads to the same destination.

[PMAT]

Two more cents. Pick a good small speaker that sounds pleasant. Add a good subwoofer and blend them. The problem with just about every other solution is that your ears won't hear the bass at low levels. The output of the sub should purposely be too high relative to flat. It won't sound right when you turn it up but it will at low levels. I heard this solution with Usher s-520's and a good sub and it was VERY pleasant at low levels and it was under $700. It also allows you to adjust the sound with the sub controls and also by moving the sub around until it sounds right. I was in a good stereo shop and walked into a room where the salesperson had turned down the amp at the end of his demo and had walked away. I was looking at other equipment and noticed how good it sounded at low volume. I played several tracks an truly enjoyed it. Let the insults begin.

[timind]

Two more cents. Pick a good small speaker that sounds pleasant. Add a good subwoofer and blend them. The problem with just about every other solution is that your ears won't hear the bass at low levels. The output of the sub should purposely be too high relative to flat. It won't sound right when you turn it up but it will at low levels. I heard this solution with Usher s-520's and a good sub and it was VERY pleasant at low levels and it was under $700. It also allows you to adjust the sound with the sub controls and also by moving the sub around until it sounds right. I was in a good stereo shop and walked into a room where the salesperson had turned down the amp at the end of his demo and had walked away. I was looking at other equipment and noticed how good it sounded at low volume. I played several tracks an truly enjoyed it. Let the insults begin.

Insults? I agree this is an excellent way to achieve the OP's goal.

[Coytee]

Let the insults begin.

ok...  "Yo Mama wears combat boots"   

As for your other comments, sounds like it works great!
 

[Wind Chaser]

How low is "low"?  Where does "low" end and loud begin?  I bet among the various answers here there are few different ideas as to what is "low" and what is loud.

[Quiet Earth]

That's why I included the rough yet reliable radio shack sound level measurements with my comments. At least it gives you an idea of what I'm talking about, if you also own such a meter.

[Browntrout]

Low level listening is defined as a volume where you cannot here all the music because if you could here the bass it would then be loud. 
  This could well be a perception issue.
  Could it be that the amount of energy per range of freqeuncy is equal but that because treble is directional and bass is not so much that in a conventional setup more high frequency energy is reaching the ears where the bass is dispersed throughout the room and therefore sounds at a lower level relative to the highs? Only an idea