imhifiman: with volume halfway up on the SLP-05 using an Audia Flight CD player the volume is very high and no distortion. So, when I say volume halfway it is to my knowledge of the system which doesn't help you much. But at halfway with the TT the volume is 3/4 of the volume of the CD but with distortion. The mono blocks are the CAD805 Anniversary.
mckinneymike: Pro-Ject evolution carbon fiber, I think, which came with the TT and a low end (I am assuming) cartridge is a Legacy. The retailer set up the unit for me. I checked alignment and the weight, and they seem fine.
On a side note, I get fantastic results at lower volume. Strings and light cymbals or brushes on the drum sound amazing.... But I still suspect you are right.