What's the greatest bargain in SET these days?

Also I wonder what the song was? If a chamber work, probably not a big challenge. If a symphony, Rush, Metallica, or a well recorded big band, I wonder if outcome would be the same?

Map,
I don't know the answers to those questions because now I cannot find that post.
I'm not worried that the De Capo's can be driven to satisfying levels with an EL34-based SET amp. My room is medium small and I don't tend to listen at live-concert levels. And Tash Goka of Reference 3A told me that the Antique Sounds Lab 8 watt 300B SET was basically developed with the De Capo in mind. Plus, if you go back and read Tim Smith's Coincident Dynamo review on 6moons, he says that the Dynamo played satisfyingly "big" even on his less efficient Harbeth's.
So at this point I'm not worried about "if" SET, but "which" SET!

As to which one to get without the opportunity to listen to any of them with the Decapos and your budget constraints, I would look at the ones with the heftiest transformers. As has been pointed out, one of the biggest factor in SET designs, what separates the budget from the pricier ones, is the power supply and transformer. This will manifest itself in better dynamics and improved low frequency performance. Over time this may be the area where by going budget you will recognize the sacrifice of performance in these areas. This is MY impression having listened to numerous SET amps in different set-ups, there is no free lunch unless you go with a more efficient speaker. The fact that you listen primarily to small scale music in a small room may mitigate this to some degree.

Agree with TG.

I have only heard SETs perform to the max with very high efficiency horns to-date, over 100db efficient, similar to Avantgarde Trio.

I heard one set fall short with Zu Essence speakers once at a show. Not with the music demoed (small scale jazz and classical works) but with music I requested as a test (Rush). This was in a typical hotel-sized guest room, not large. The lack of dynamics was noticeable even at moderate volume to me.

DeCapos are less efficient than Zu I think.

So any of these may well work in many cases, but seems to me the beefier designs will have the one-up.

Rebbi, BTW, after the Zu/SET demo with some challenging rock music, the ZU guy doing the demo admitted the amp was underpowered for the task most likely. I wish I could remember what amp exactly was used, but do not. I don't think it was any of the main contenders here.

It registered to me that Zu seemed more interested in marketing how well their speakers can do with a flea powered amp than they were with showing them off at their best.

On the other hand, I heard a Jolida FX10 do very well running a small pair of Nola monitors another time, with sound that hit way above what I expected. However, those were small monitors with limited low end extension and I think that was the difference. Your DeCapos are much bigger hitters in terms of low frequency extension I believe and I think that is where the challenge will come in some cases, if its something that might matter for you.

The compromise I hear in lesser cases is more about dynamics than volume, though certainly volume can be an issue as well.