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

The lower power only means peak SPLs will be more limited in general and that may or may not be an issue depending how loud they need and how far from speakers they will be when listening. 40 watts can drive many speakers to decent levels and if a tube amp the amp will likely soft clip if overdriven which is good thing. Some or maybe most Class D amps will soft clip as well.

An easy load will help any amp perform it's best, allowing decent SPLs with minimal watts. I’d add Fritz or Ohm Walsh for that myself. Two very good and very different additional ways to go.

Use this calculator to help assess speakers based on efficiency.

Crown Audio - Professional Power Amplifiers

I  picked up Heresy IV's open box from my local retailer for $2500. A little.over your range but highly sensitive and.a great match for a tube source. Highly recommend if you can get a used pair.

You need to find a vintage 16 ohm american speaker made prior to 1965 to experience low power tube equipment properly and when you hear one you will never go back to new speakers on any music.

I second the recommendation to consider Monitor Audio, specifically the Silver 300.

I love my Martin Logan Motion 40’s, but Salk would be as good choice too….