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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after 49 yrs, I realize these Seas Magnesium midwoofers are excatly what I was looking for,,and soon to add a  Crescendo tweeter. 
I can't think of a  better combo, Dual W18's, But since you are starting from scratcgh, go dual W22ex. more bang in the lows. 
w22's are low sens . well lets say avg sensitivity, , 8 ohms, 87 db, the Crescendo at 6 ohms/92db
40 watt tube = easy drive w dynamics. 
I’ve been driving 89db speakers with a pair of old tube amps that are 20wpc in triode, and 35wpc in ultralinear mode. I typically use triode for the preferred sound quality, and almost never feel I lack power. It plays loud enough to disturb my wife and kids. It depends a lot on the room and their preferences, but average sensitivity isn’t a liability for many folks, which opens up many other outstanding choices.

Wharfedale, Monitor Audio, KEF would be on my audition list for them to see and hear.
Ascend Acoustics for new tube friendly speakers. Also Zu Dirty Weekends for a fun less refined sound.
For those that enjoy projects eBay has a wealth of vintage JBLs ready to refurbish.
Great suggestions so far. Thanks. TMR has an Omega at the moment, the only situation in which one can *try* an Omega. Ascend Acoustics popped to mind for me, too, but I have not looked at their specs. Mozartfan's list of ingredients will be helpful if my friends want to climb the DIY learning curve, otherwise, they'll need a Rosetta Stone.