Did I buy a broken amp?

I purchased a used amp to mate with a dac / preamp in the same line which I own. The new amp is suppose to be 150 watts into 8ohm.  When I play the amp at 35/100 volume, I barely hear any sound.  I need to get volume  to at least 75/100 or 80/100 to provide adequate listening sound. 75/100 sounds how 50/100 should sound. (And so on)   It does not seem to clip or distort.   Could the amp be broken or does it just not provide enough juice for my speakers? 
Preamplifier / Dac Wadia 321
amplifier:wadia 315 
Apple TV source 
speakers: Kef 201/2
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.

-- 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.
Thanks guys.  I think you are all right in the money. The speakers are very inefficient at 85/86 and it sounds like Wadia did not want to offer much headroom through their design for whatever reason.  At 88 the unit is satisfying enough I suppose.  I think the speakers still need to broken in some as I bought them new old stock recently.  That’s probably another discussion though.