Speakes for SET amp

I'll second Coincidents - I use Super Eclipse III's which worked great with my 300B SET amps. Their newer speakers are very positively reviewed in the recent TAS (Victory line) are in your price bracket. The woofers are not "powered" though - if you were looking for that you'd have to go the route of a sub. Another really great candidate, although I think they exceed your budget and rarely come up on the used market, are Classic Audio Speakers.. I've never actually heard them paired with SET amps, but the Audiokinesis speaker line are fairly efficient and have sounded outstanding to my ears the two times I've heard them. Contact Duke to see how they may pair with your amps. Another outstanding candidate which I have heard paired with a 211 amp is Daedalus Speakers.

Zu, Klipsch, Coincident... All very different,

Definitely very very different. I tried a pair of Zu Definitions in three different systems in my own home for a week and heard them again in two other friend's systems. Absolutely hated them, including with my SET amps. Klipsch from the Heritage line would be great, but the best versions of those are very large and require quite a bit of tweaking to sound their best (much direct experience there as well). Once honed in they can sound magical with SET - if you have the space to make them shine, and a bit of extra time and willingness/ability too, that's a brilliant combination if you don't mind the retro look. Coincidents are great right out of the box with nothing to do but proper positioning. I tried finding a conventional dynamic driver speaker that would satisfy me after years with the lightening fast horns on my Klipsch LaScalas (heavily modified). Coincident is where my search ended - not quite as quick as horns, but mighty close and certainly of the fastest dynamic speakers I've heard in the high-sensitivity realms. Disappear like monitors, and also do very will with SS if you choose to switch (at least the model I use does - not sure about the Victory line as the tweets are radically different). I so don't get why anyone would like Zu though, at least the Definitions...just my own experience with them. Bottom line - try to listen to some of the options yourself and see how they occur to your ears.

Check with member, Tvad, on the Audio Note speakers. He just recently got a pair, I think. I don't know what amps he's using with them. He has plenty of experience to give you some perspective. I'm not sure how his taste in music crosses over with your own. Atmasphere OTL would be another great direction to go as far as amplification, IMO, and may offer more versatility than many SET options. Ralph's amps are outstanding. But it sounds like you are happy with your 211 monos (which I can understand having spent about six years with SET amps). I would make your upgrades with the utmost care at how your specific amps (or the ones you will buy) pair up with the speakers you buy. That link is critical.

Nakonawala, have a listen to the Avantgarde-Acoustic Uno G2.

Hmmm, isn't that a $27K speaker? If you are getting into the realms of big German-horns don't miss Acapella for another price leap. In the two shows I've listened to both extensively I was consistently amazed by Acapella, whereas Avantgarde just didn't do it for me though the model Jtein suggests was not what I heard (I listened to the Trio and Duo models). In those cases I was far more impressed by the more modestly priced offerings from AudioKinesis and Daedalus that I've mentioned. That certainly could have been the room/systems they were each in. As we all know, those hotel show rooms leave a whole lot to be desired as far as being an agreeable acoustic space. Some systems seem to be far better at seemingly overcoming that obstacle than others, and Audiokinesis sattelite sub system was certainly among those. Two others that impressed me in that way, though not at all SET friendly (so not suggesting them to the OP), were Roger Sanders panel speakers, and those weird little toilet seat speakers that I almost entirely ignored because of their appearance...Gradient Helsinkis. Both of those seemed to completely defy the otherwise horrible rooms they were set up in, as did Duke's Audiokinesis offerings. Daedalus was in what looked to be a less challenging space, and also was a big standout for me. Anyway, I'm not suggesting you ignore the good suggestion above. Add Acapella to the list if you are going to start listening to speakers outside your budget and want to hear what great horns sound like. My own experience with horns suggests they are best with space around them to allow them to breath, and are very challenged by confined spaces. The Acapella model with a separate sub is the Triolon. I'm afraid it's also well beyond the stated budget of $8k.