300B Speakers, Reynaud & Reference 3A

Many of the Audio Note speakers would do the trick. I would suggest you contact Joe from JC Audio and get his advice.
These speakers are based on the old Snell design and have between 93db and 95db sensitivity with an easy amp load. They will work very well with 300b's.
They don't look like much which is why I believe they are often overlooked but they will outperform many speakers at much higher price points.

I've driven my JMR wins with a Cary SEI-300B and it worked extremely well on most music. In fact, I'd say it was jaw dropping - rich midrange, airy highs, and deep articulated bass. The most amazing vocals and acousic instruments that I have ever heard on my speakers. As mentioned above, can't be beat for small jazz, chamber music, quartets, etc. And it could go L-O-U-D.

Depending on the size of your room, musical taste, and how loud you like to listen it could be a match made in heaven.

The problem I found was that the Cary ran out of steam on complex passages. It was like the music collapsed inwards on itself. All bass whatsoever disappeared. Some knowledgeable SET fanatics told me that this was probably more a power supply problem of the amp than the low wattage.

You really need to hear the matchup for yourself before deciding. SET + Twins is a magical combination. Although, matching the JMR speakers with just about anything is great. Of course, I'm horribly biased :o)

Tom, just for reference, did you listen to Lowthers that were 1 year old or more? There have been major changes to the Lowther drivers in this past year. The model names remained the same. They have rolled the suspension surround inwards for smoother response, and have put a rolled edge on the whizzer cone to virtually eliminate the upper midrange anomalies known as "Lowther shout". It is a much more refined sounding speaker now. After about 200 hours of break-in these speakers are very fine sounding units. Perhaps another listen, with the new drivers?

Twl...The speaker drivers I listened to were at least 3-4 yrs old. They were both in homemade cabinets. I don't think there are any dealers in my area (Southeastern Michigan) who carry anything with Lowther drivers, don't know how else I could get a listen to something new. I also still think that, at 100db efficient, the system might be too noisy for my liking. I'll check some Lowther websites, however, and see what's happening.

Tom:

Another candidate may be the smallest Galante speaker ($2500-$2800) new. I have no experience with it myself, but it has received favorable reviews (both for its sound and low wattage capability).

I think that it is a coaxial design (tweeter mounted in the center of the LF driver) which usually works quite well in close spaces.

Don't know if this interests you, but I plan on building a pair of single driver speakers (for the 2A3 amps) using vintage Stephens Trusonic 8" drivers. I was considering new Lowther drivers, but (as you mentioned) I do not feel that my Bottlehead gear is quiet enough to make a good match.

The Abbey speakers (mentioned above) are single driver speakers (using Fostex) that are based on the Voigt pipe design (same as TWL's speakers), but they are well below 100 dB efficiency. The last time I checked the Cain & Abbey website they were offering a "near field" version of the speaker that might be suitable for your room (depending on the layout).