SET amplifier recommendation

Line Magnetic, KR and NAT. NAT makes some incredible sounding SET gear that used may fit your budget and will drive the snot out of those B&Ws.
Good luck!

I have an idea that might work, emphasis on the word might. This amp right here: https://diyaudiostore.com/collections/amp-camp-amp/products/amp-camp-amp-kit?variant=7072933085218 is an easy to build single ended transistor kit. It sells for $327, but if I recall shipping is expensive because the case comes from Europe somewhere. It is designed by Nelson Pass, and has a true single ended sound without the impedance and damping problems a triode tube would have, but it is still only 6 watts. Although I bet this amp would drive your speakers, it would not be ideal. I agree with the consensus that different speakers would be a requirement for true single ended nirvana. The trick is; it is a few hundred bucks rather than a few thousand and it would give you a taste of what the single ended craze is about. You would have to learn to solder if you don't know how already.

After I built my first S.E.T. amp (45 tube, 2 watts per channel), I spent 20 years looking for a true full range speaker for it. I wound up building a large, make that very large (even I wouldn't have it in my living room), Altec based horn speaker with a RAAL ribbon tweeter. The system is tri-amped. I use this amp right next to my S.E.T.s ,for driving the tweeters.

@jdl57 A speaker change to Coincident PREs (from Coincident Super Eclipse IIIs) caused me to have to change amps from Coincident Frankenstein 300bs.  Eventually I built my own First Watt F4s and find them excellent.  I was very surprised, because I had previously demoed a Pass Labs XA25 and did not end up keeping it (although it was excellent). 

The F4s are certainly not SETs, but surprisingly, I don't really miss my Franks at all. The F4s create a ton of space and have excellent tonality.  A touch of sweetness while also being incredibly transparent.  They don't distort at all and play better at the extremes with the PREs (94db and supposedly a flat 8ohms).  Plus, as you point out, DIY does save a lot of money.  I built two monoblocks and vertically bi-amp my speakers so each driver gets its own 25 watts.  Under $1800 total cost.  I sold my Franks and upgraded tubes for around $4000.

@cygnus_859 Also, I know DIY isn't for everyone, but if it does sound at all attractive, I would just ask the community over at:  https://www.diyaudio.com/forums/pass-labs/ which amp build would best fit your speakers.  A lot of very knowledgeable people over there (including Nelson Pass himself).  I kind of wonder whether they might recommend an amp with light feedback for your speakers... 

@jdl57  6 watts isn't going to do it on the 805. Quite simply you need some power.