SET with inefficient speakers

On their website Dali claims to have a very flat impedance curve. If so, you'll be able to drive your Dali well with a 10wpc SE amp w/o much problems.

BTW, I drove 88db efficient speakers with a homerolled 2.5 wpc amp and the bass was astonishing. Much better than a 50wpc Nad I normally use to run in speakers or to hold the door open.

Check out Dehavilland's SET amps. They are higher powered than most SETs, and designed with the goal of being compatible with many speakers that otherwise wouldn't work well w/SETs. Their website and all your basic research will give you plenty of info.
I am using their 30w Aries 845Gs to drive Alon V speakers that normally recommend much higher power. Most listeners can't believe that I'm driving them with SET amps. Cheers,
Spencer

After owning all types of gear (some very expensive and powerfull) I have downgraded to the diminutive Shanling MC-30 receiver (absolutely fantastic value). Tube preamp, SET 3-watt amp (yes, that's SET!), cd player and tuner all into a single stunning chassis. All for not much money. Actually, the cd player alone sounds like twice the price of the whole unit. I had purchased this to use it only as a cd player to be paired with some powerfull monoblocks. When I tried this gizmo on its own, with no power amps, I just could not beleive the proverbial jaw-dropping sound with just 3 watts....sort of makes a lot of other gear look overpriced to me right now.

Paired with my 89db Opera Quintas, I get great, full sound at low-moderate volume.

My personal opinion on the subject:

If it sounds good, it is easier to accept power limitations.

If it sounds bad, power won't make up for a better experience unless one likes noise.

Good luck.

its not impedance alone that will get you, but rather a combination of low impedance AND hi phase angle. Meaning a highly reactive load.
More info on the speaker, including some real measurements would be helpful.

I prefer low impedance, a 180 degree angle, preferably on a sofa, phase-reversed continuous ohm calibration along with a non-reactive by-passed load of no more than 100 cryogenic microfads wrapped up in double-wound 100% oxygen-free copper, originating from planet Krypton.

Another route, a bit simpler maybe, would be to just sit-back and relax with a glass of wine, forget hi-fi and enyoy music...and life!

No offence intended, with a grain of salt !