SET amplifier recommendation

The issue of bandwidth becoming more limited as the total output power is increased happens with any amplifier with an output transformer. In SETs this issue is exacerbated.

Thanks, Ralph. That would say that in the case of tube amps having output transformers published frequency response specs should be taken with grains of salt, unless the power level they correspond to is clearly stated (with that basis preferably being full power). (And also, as with the frequency response or bandwidth specs of any amplifier, grains of salt should be applied if the amount of rolloff the stated response corresponds to is not indicated).

And if I may say so, the specs provided at your site are exemplary in those (and other) respects.

Best regards,
-- Al

I recently built the Elekit TU-8600R-VK with Lundahl OPT's and TKD pot.
I'm running Gold Lion PX300B, Tele 12AX7 and RCA Cleartop 12AU7.

It is sublime!!! Amazing amp and would costs $1800 for the upgraded kit, a few hundred more for the tubes I mentioned, or you can go with EML or Elrog 300B within your $3000 budget.

Not that it matters too much but Herb Reichart reviewed it for Stereophile and compared it to $20K amps, landing into the list of recommended components.
https://www.stereophile.com/content/gramophone-dreams-27-elekit-tu-8600r-amplifier-kit

Do NOT buy anything from Coincident. I made that mistake a few years ago, and will never consider it again.
the dynamo is a cheaply made Chinese crap, with the cheapest parts and terrible workmanship. I’ve had issues with it from day 1, and the customer service I received from Israel was appalling. He did not own his warranty for an amp that arrived defective, tried to blame me for it, and wouldn’t even pay for return shipping for the repair, even though after I sent the amp back he admitted that it was faulty. If you want a Chinese SET, get a cheap one one on eBay. Quality will be the same, price will be 1/4 of the dynamo, and most Chinese sellers provide customer service orders of magnitude better than Israel.

I have tested a B&W 805 with an Ayon Mercury 300b Set amp (20W). Very bad match. 

You have gotten plenty of input, but I thought I would chime in because I have 805's and have hooked them to many different amps.  The sensitivity is definitely an issue.  I have had them hooked to even some higher power tube amps(not SET) like Cary, McIntosh, etc, and they just didn't sound good.  They definitely sound significantly better with more power.

As far as replacing them, if you really like the B&W sound, you won't be happy with vintage Klipsch, IMHO.  But getting new speakers is a whole different ball game :) Good Luck!