Did I buy a broken amp?

  It does not seem to clip or distort.   Could the amp be broken or does it just not provide enough juice for my speakers?

What happens when you turn it up all the way? Can you overload it- does it get loud enough? If yes to both, its fine- that's just how it was designed. You could contact Wadia- there's a good chance they know the answer :)

At 100/100 it is pretty loud for book shelf speakers but usually I expect that kind of loudness at 70/100 with unknown headroom beyond that. Perhaps it was the way it was designed.  I’m just surprised that it seems barely audible at 40/100 volume level.  I can try the speakers with another 150 watt amp later this week to see if there is much of a difference but I guess that probably won’t matter much as it may go to the Wadia design. 

Don't know if you have access to Ground and In tap hole on volume pot to run in series 2 resistors. My  Preamp with goldpoint stepped pots 9:00 was my preferred loud listening level now am at 3:00 to be at preferred listening level by adding 2 resistors. I may tweek resistor value a little. I'm now where you are on volume position level and like it. It's strange to be at 3:00, I'm use to being between 11:00 and 1:00 but as long as I have headroom before distortion I'm okay. My problem was there was to much gain between each step and could not get sweet spot on volume level, now I can. I used the Takman carbon resistors I was told they were warmer than the metal, I also thought they made the amp sound a little better, maybe who knows. 

The following statement appears in the manual for the Wadia 321:

A Volume Setting of 88% on the Wadia 321 will provide optimum performance when it is connected to a Preamplifier (Integrated Amplifier or Receiver).

Also, Stereophile measured the sensitivity of your speakers as being a rather low 85.5 db/2.83 volts/1 meter.

Both of those facts seem consistent with the need to utilize the Wadia's volume control at relatively high settings.

Regards,
-- Al
 

YouTube has an in-depth documentary on the importance of the volume control. Its only a few minutes and well worth the time. Search for Spinal Tap ours goes to eleven.