I've tried a few things in the SET area, regarding speakers.
The first thing is that nothing replaces high efficiency/sensitivity when you go to low power amps. You need to get as high sensitivity speakers as you can. This gives you more headroom, and reaches deeper into the detail.
Regarding the Hornshoppe speakers, they are nice and made pretty well, and sound pretty good. But I have used FE103 drivers in a few designs, and they just don't get into the bass very well, and what bass they do produce is restricted by the very small amount of air that a small driver like that can move. You will find that they lack in the bass.
When I switched from FE103 based speakers to Lowther EX3 based speakers(Voigt Pipes), the difference was staggering. Better all around sound, much more headroom, gobs more bass, way more detail, just way more everything.
I'd agree that the Cain and Cain Abbey speakers would be a good try for your under $1k budget. They are a Voigt Pipe design, and have the single-driver advantage that mates well with SET amps. However, the Fostex drivers will not sound like a Lowther, and although they are good, the Lowther drivers are way better. I made my Voigt Pipes myself(very easy to do), and spent my $1k on the Lowther drivers. I made a few custom changes to mine, and drive them with my Berning 45 SET-ZOTL(2 watts per channel) and an analog front end. Very awesome results down to about 40Hz on the bottom end. Max SPL peaks at around 106db.I really don't notice any "lack of bass" with this system. It is so good at doing 40Hz and up, that the few things that actually occur below 40Hz don't make a difference in my enjoyment. Of course if you are a pipe-organ fan or something, you'll need a sub. I did make some mods to my cabinet which overcomes the baffle-step losses which are typical in this type of system, so my bass is better than other Voigt Pipe designs.
Regarding your comment that Lowthers are too expensive to experiment with, you can just build an easy cabinet like a Voigt Pipe, and you can be good-to-go for under $1500/pr complete with Lowther EX3 drivers.
The down-side is that they are pretty large, and may be a bit taller than your size requirement dictates.
The first thing is that nothing replaces high efficiency/sensitivity when you go to low power amps. You need to get as high sensitivity speakers as you can. This gives you more headroom, and reaches deeper into the detail.
Regarding the Hornshoppe speakers, they are nice and made pretty well, and sound pretty good. But I have used FE103 drivers in a few designs, and they just don't get into the bass very well, and what bass they do produce is restricted by the very small amount of air that a small driver like that can move. You will find that they lack in the bass.
When I switched from FE103 based speakers to Lowther EX3 based speakers(Voigt Pipes), the difference was staggering. Better all around sound, much more headroom, gobs more bass, way more detail, just way more everything.
I'd agree that the Cain and Cain Abbey speakers would be a good try for your under $1k budget. They are a Voigt Pipe design, and have the single-driver advantage that mates well with SET amps. However, the Fostex drivers will not sound like a Lowther, and although they are good, the Lowther drivers are way better. I made my Voigt Pipes myself(very easy to do), and spent my $1k on the Lowther drivers. I made a few custom changes to mine, and drive them with my Berning 45 SET-ZOTL(2 watts per channel) and an analog front end. Very awesome results down to about 40Hz on the bottom end. Max SPL peaks at around 106db.I really don't notice any "lack of bass" with this system. It is so good at doing 40Hz and up, that the few things that actually occur below 40Hz don't make a difference in my enjoyment. Of course if you are a pipe-organ fan or something, you'll need a sub. I did make some mods to my cabinet which overcomes the baffle-step losses which are typical in this type of system, so my bass is better than other Voigt Pipe designs.
Regarding your comment that Lowthers are too expensive to experiment with, you can just build an easy cabinet like a Voigt Pipe, and you can be good-to-go for under $1500/pr complete with Lowther EX3 drivers.
The down-side is that they are pretty large, and may be a bit taller than your size requirement dictates.