I'm just going to put some technical thoughts down here, see if I can get back to the specifics of what John needs for his system.
I'm not a big fan of heavy-duty bass in the sub 40Hz range myself, either. I do find the subject of how to do quality bass ( and not necessarily LOUD either ) in the 35Hz to 80Hz range, to interface properly to Electrostats or Horns, VERY interesting. I haven't done enough work in this area yet to have fully-formed opinions, so it's good to have some discussion. The same range is also of interest if you're going to deal with the mid/bass driver compromises by building moderated-size sealed box monitors, which have some obvious advantages. By freeing-up the lowest octave, you make life simpler in some ways but the task of getting a well-blended bass solution is not trivial.
We've mentioned OB, and I like OB bass if done right. I'm going to upset Ali here ( most likely ) by saying that my scepticism about the Eminence Alphas is not helped by you telling me you used twin Alphas on your OB solution - which I heard a good while back to be fair. Now, it could be how you used the DSP, but I wasn't entirely happy with it, and it was something of a feeling it was a bit loose or uncontrolled that I didn't like .....
In my opinion it's a lot better to go with the Betas and let the OB design ( eg. with some side wings ) and either series resistance or a series choke help put the Q up towards the ideal 0.7 value.
The other option , rather similar is the extension of the OB idea that Heil and Nelson Pass originally developed ( I think - Richard may correct me ) , with slot-loading at the front. Taken to its extreme it becomes the 'Ripole' concept, but I feel the Ripole is pushing things a bit, with so much cancellation around the sides, it's pretty inefficient and this can give rise to some problems as a number of postings on threads over the last few years have shown.
I'd prefer to see something with more substantial side-wings , as in the very good summary Nelson Pass provides here :
http://www.firstwatt.com/pdf/art_slob.pdf
This is essentially the same thing that JC Morrison has built a couple of times for the big WE horns systems for Joe Roberts ( Silbatone ) or at the recent ETF.
Now it would only take a single pair of drivers to do something useful in a normal sized room, for augmenting electrostats , so it would be nice to see someone try that.
The key thing to get any of these things to work is how the phase behaves in the crossover region. With electrostats I suppose the phase rotates slowly and smoothly as their response tails off , like OB or a sealed box. This must be helpful. For horns it's more tricky as they tend to fall of a cliff edge , but I know that JC regarded the slot/baffle bass at ETF as being the most successful he'd ever used on a horn system , which is encouraging.
"Once you find out ... the Circumstances ; then you can go out"
