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.
128x128hilde45
+1 on what speakermaster said. 
For DIY look at GR Research. Danny has some amazing stuff, most very efficient. I have XLS Encore, and they are crazy good for less than $1k with flat pack box kit and every crossover upgrade offered. 
Don’t rule out designs like KLH model Six, Advent large, and Warfedale models. I rebuilt a pair of model Sixes eliminating the tweeter level switch, using nice mid level crossover components, and they are jaw dropping with 12 watts of EL84 power. Most of these models would likely perform admirably with similar upgrades. 
You can’t really begin to narrow the field till you add room size, music genres taste, and desired listening levels. My room is small, and I like rock. I doubt I use more that 2 watts in normal listening, that give me plenty of reserve power for dynamic swings. 
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.