Efficient, affordable speakers for SETs?

A second for some of the GR Research models, the Super V if you can find a pair. It is comprised of a coaxial mid/tweeter and the remarkable OB/Dipole woofer.

@stereo5  Sandy is also one of our customers and has an S-30, which he uses on his Quads. BTW his Subx subs are quite good.

I have some experience with 3 different sets of affordable efficient speakers, some mentioned above.  The amps I've run are a 3.5 wpc 2a3 SET and an 11 wpc EL34 SEP

1) Tekton Perfect SET - Clean, clear, and powerful.  Nice deep bass, powerful dynamics, and excellent imaging.  They can fill bigger spaces with full range sound very nicely.  I did upgrade my caps and the improvement was great, I highly recommend the upgrade for high end SET enthusiasts.

2) 8008-Corner by Troels Gravesen - Similar to the Audio Note E, simple efficient 2-way kit with top quality parts.   These are 92db eff., so on the lower end for SE amps, but the impedance is very flat and super easy to drive.  (AN-E have overrated efficiency, so these are very close, Troels's article explains this)  These are my top speaker, but best in smaller rooms and with corner placement.  These have a vibrant, rich, and vivid realistic sound that performs very well with SE amps.  Bass won't fully rival the Tekton, but it's there and they go very deep for a smaller 2-way.  Daft Punk is a joy with my 11w SEP and not bad on the 2a3 either.  I think the smaller transformers of the 2a3 limit the deepest bass.

3) Lii Audio F15 - Just got these and still need to build a baffle, but I'm starting to like them.  They tried to tear my ears off with any volume at first, but they are settling in nicely after 4 days straight of run in.  I think I'll like these better than other OB or Full Range single driver in the end.  I also think they will need a sub to play as deep as the other 2 speakers above, but the baffle will certainly help too.  There is still a bit of coloration from the whizzer cone, but not too bad and it might still get better with time.  I'm really liking the big sound stage, excellent detail, and nice kick the 15" woofer has in the mid bass.  I'm planning to build some flea watt amps to power these, should be fun.

A note...Dennis Had is back with SEP (he's lately been doing mostly lower powered SETs...my amp is a pentode model) amps on Ebay that seem to be orderable as he notes different color face plates are available. He's added a stereo volume pot but I imagine you can get him to eliminate it maybe...a world class hand made amp at a bargain price IMO...note I have no affiliation with Had except my daily astonishment at how good my Had amp sounds.

I have a Dennis Had KT150 SEP and his LP-3a preamp, but I don't use them much any more.  I built the P134B designed by Jack Elliano of Electra-Print with all top grade parts.  Parts like Jupiter coupling caps, Audio Note Silver Tantalum resistors, AN Kaisei caps, VH Audio OCC wire, and more.  The transformers that Jack wound are MASSIVE in comparison and you can tell the difference in sound.  The sound is rich and vibrant with deep powerful bass.  I don't want to step on any toes, but I can't go back to my Dennis Had.  His are understandably built for an entry level single ended price and couldn't possibly put the parts I used in and make money without charging $3-4K.  The DH amps are a good start and really got me into the magic of single ended, so I certainly wouldn't fault them.  I might upgrade the caps in mine and see how they do, I do really like the flexible tube rolling they offer too.