Speakers for triode tube amps

I'll toss Monitor Audio into the mix. 

If you are a fan of the Harbeth P3, I think you will like the Falcon version of the LS3/5A.  I have heard it, the original BBC 15 ohm Rogers LS3/5A, the P3 and the ProAc Tablette in the same system.  I like all of these speakers, but, I slightly prefer the sound of the old Rogers and the Falcon (warmer and better midrange than the other two).  I know both are quite inefficient, but, they are an easy 15 ohm load and I heard them with low-powered amps; in fact, in one comparison session, the Synthesis Roma 96 amp was used and it is rated at 25 watts/channel.  If a small monitor is in your plans, the Falcon is something to consider.  

Another reasonably priced, very efficient speaker to consider is the Rethm Bhaava.  This speaker has a built in powered woofer, so your amp will only be required to driver the very efficient main driver.  This is a quite lively sounding system that is a nice change from the sound of the Harbeth 40.1s.  

@larryi2  In the day, Magnepans were marketed with either a D-76 or D-76A when it came out, or bi-amped with D-51's and D-76 amps.  

Yes, the more power the better with Maggies.  I realize there are many lower-power tube amps and no, Maggies do NOT perform at their best at higher volume with ANY lower-powered amp.

If I misunderstood the OP's post, I am sorry. So, for clarification, IF you want to pair good tube amps with Maggies, be sure you have the most power you can afford.

Cheers!

My vote would be for Klipschorns. 

+1 for corner horns.  If you got corners they bring the heat