What speakers work with low wattage class A amps

I'll second @akg_ca

The de Capos are great speakers, I have the earlier de Capo i in red maple

FWIW

this month's Stereophile has a review of the Heresey speakers, which are super efficient. The reviewer used a couple flea 2-3 watt amps then used a Parasound 21+ (400wpc@ 8 ohms) which had more balls and sounded more organic

I would think very reasonably priced GaN amps (by comparison to class A) are worth investigating

The Klipsch Heresy IV is the best LIVE sounding speaker that 3K will buy. The soundstage goes wall to wall and I run them with a 2.5 watt Decware amp OR a 400 Watt Gan Peachtree amp.. They sound fantastic with both. Also Tekton Pendragon w/ 7 tweeter array sound wonderful.

What you can drive with 25 wpc depends a lot on how large a room you have, how close to the speakers your listening chair is located, how load you play your system, and how much you are willing to compromise on sound quality during the very brief moments that you actually use close to the 25 available watts.  I personally value high quality sound at relatively low volume levels, and I find that high quality low-powered amps tend to be better at lower volume levels than even ultra-expensive high powered amps.  

Still, with only 25 wpc or so, it would pay to emphasize higher efficiency speakers.  Among the very best high efficiency speakers I've heard are the Charney Audio Companion line of speakers.  These come with different choices of driver (all are good but I particularly like the AER driver).  I like the Fyne Audio line of coaxial speakers and they are quite efficient.  The Audio Note line of speakers are also quite good with this level of power.  Devore Orangutan speakers are also fairly easy to drive.

It has been a long while since I heard the 700se, but I am quite familiar with the 30.2 speakers.  I know Harbeth recommends high-powered amps for their speakers, but, I really like them with modestly powered tube amps.  I particularly like them with the Synthesis A40 amp (40 wpc, two KT66 power tubes per channel, integrated amp with a terrific built-in DAC).

As always I think amp-speaker matching should start with finding a speaker that locks in well with your room.

But if you want enjoy 2A3, 300B, and 845 SETs the Heretic line of speakers made in Montreal are guaranteed to work. 

And, of course, I've been using LS3/5a with SET 300Bs for 35 years.

So those are two non-horn recommendations.

enjoy the adventure

herb