Speakers that are good with tubes

@noske You can have a 4 ohm nominal speaker sound just fine running the 8 ohm tap on a tube amp.  My experience has been you just have to try and see what sounds best.  Even the manufacturer will say this.

Tubes, typically at least, give a warm sound that had absolutely nothing to do with efficiency of the speakers themselves. Current of your tbe amp would be more important than power. But assuming a typical audiophile 100-200w tube amp you can drive any speaker. For tubes I'd always recommend Magnepans, and which would depend on room size. They will sound great with a tube's warmth (and let's not forget different tubes have different sounds on different amps). And I don't think you specified, I am assuming a tube power amplifier or integrated. If it's pre like my CJ, it would further depend on if you have tube power or SS. 

In my humble opinion, I can't ever picture myself pushing Klipsch speakers with anything OTHER than tube amplification -- to me that combination is just a match made in heaven.  I am not that familiar with a wide variety of horn speakers, but music lovers I've spoken with over the years always seem to pair tubes with horns.

I understand the value and intrinsic benefits of smaller tube per amps.  In my case, I opted for power and have a pair of McIntosh  MC3500 Mk2 power amps being driven by a McIntosh C2700. I am running Focal Scala Evos which sound great, but what are other speaker options?
 

You can have a 4 ohm nominal speaker sound just fine running the 8 ohm tap on a tube amp. 

@tubeguy76 With full knowledge that the tube amp will have to produce twice the power that it was designed for.  This is not a risk I would consider to be prudent.

Are you prepared to name the manufacturers who said it is safe?  How about running a 2 ohm speaker from an 8 ohm tap?  That may sound just fine, too, until smoke appears.