Reasonably sensitive speakers for tube amps, max $2k/pair, new or used


While this topic has been covered before, I'm interested in both recent experiences with new products or anyone who just would like to chime in.

I have a couple friends interested in tube amps, lower wattage -- 40 wpc or below. Before they pull the trigger there, they need to find the best higher sensitivity speakers they can, hopefully at $2k or below, new or used.

QUESTION: What high sensitivity speakers would you recommend to them, new or used? What did you try and NOT like?
Characterizations of their sound, experience with a trial period, the company, etc. appreciated.

I'll pass the best answers and links along to them.
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Try Alta Audio I/O.  There still may be some left,because they’re discontinued. Originally $3.500 can be had new from Alta for $2,500.

Look into Audio Nirvana drivers. You’ll have to build/or have someone build boxes for you. Once installed you’ll be amazed. Quite a bit under your budget aswell. Outside of that id be looking at Tekton Perfect Set. Would love to hear a pair of these as I'm a SET guy. 
Strongly recommend the Omega alnico lines. In your budget for monitors, I enjoy my Custom CAMs like no other before it.