Could your TuneBox may need more gain...Is there a gain switch (MM/MC), and if so, is it correctly positioned for the Shelter? Have you tried a line input with your Pathos? Plug in a CD player to see if there is a similar problem there. If you don't have a CD player try the audio outputs on your DVD player or any line-output. At 88.5 db efficiency your Virgo's should not present too much of a challenge to the 70 watt integrated, but a larger listening room may add to that challenge. Still, it shouldn't be that far off as you describe.
Marco
Marco