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

Tekton but don’t return them or you’ll regret it. The owner is a prick and doesn’t care what nice you decide to return. 
Zu is super patient and takes returns no questions asked. They make really good matches for tube amps just take care in your tube selection to maximize the good virtues and minimize the bad. I found 6922 tubes and KT66 in my Decware amp to produce the best Sonics and balance with none of the distortion or shout that they can have. 
Used try spatial audio. I ended up with these after Zu and love them 

@tvad 1+

"Tekton but don’t return them or you’ll regret it. The owner is a prick and doesn’t care what nice you decide to return".....seems the flavor of the month in low fi speakers is finally getting exposed as the junk they really are along with their bs send em back you pay big bucks policy.

Just bought an open box pair of Heresy IV for $2,200.00. 

+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.