@fosolitude I think its a good idea to replace your Joseph speakers, which are good speakers but simply not efficient enough to really take advantage of what the Jota does. To do that, the speaker should not expect the amp to be pushed past about 20-25% of full power. A friend of mine has that amp; when I tested it, it made about 18 watts.
The Classic Audio Loudspeakers Hartsfield is a speaker that has the efficiency to work with SET power since its about 105dB/1 watt.
But you might consider an alternative- first, high efficiency speakers often trade off bass extension for efficiency and otherwise might be enormous. So what I would do (even if not using high efficiency and also since getting that bottom octave is really expensive with high efficiency speakers), is to set up a Distributed Bass Array to take care of your bass up to about 60Hz. At that frequency getting it to blend with any speaker is a walk in the park. The Audiokinesis Swarm is a great way to do that, and it would be driven by a subwoofer amp independent of the Jota. Talk to Duke at Audiokinesis about this- but do it- this will make the whole thing a lot easier!
Since it would be doing your bass, now you don’t have to worry so much about the bass response of your main speakers which will be driven by the Jota. All you have to do is find a speaker that is good to 60Hz or so and there are plenty that can do that. The harmonics of the bass instruments will convince you that all the bass is coming from the main speakers. The only caveat here is that the speaker will still be getting a full range signal which the Jota will be also playing, so that speaker should be able to handle that even if it can’t reproduce it.
Some of the smaller AvantGarde speakers (Uno or Duo) would do the job and they are not sensitive to the room. An advantage of horn speakers is controlled directivity of the horn, which allows you to reduce side wall reflections which can otherwise cause harshness.
You might also consider some of the so-called ’full range’ speakers using a Lowther, Cube, PHY, Feasterex or similar driver- with the understanding that such a driver will need a tweeter (probably rear firing unless a crossover is used) to insure that you don’t have beamy highs requiring your head to be locked in a vise :) ZU Audio makes such speakers. The ’full range’ drivers won’t be as efficient (96-99dB is typical), but the enclosure they are in will be smaller, unless they are used on an open back baffle.
Spatial Audio and PureAudioProject are both examples of nice open baffle speakers that are easy to drive, although you might be able to run the amp out of gas on them at high volume. But they are a good 6-8dB more efficient than your Josephs and that translates to as if you have an amp that is at least 4x more powerful.
Finally, pay attention to the speaker’s impedance and avoid 4 Ohm loads! Ideally you’ll want to find a 16 Ohm speaker since that will allow the output transformer of your amp to be more efficient and will also allow it better bass response (you can lose an octave of low frequency bandwidth of almost any output transformer simply by using the 4 Ohm tap).