I have the Treo CTs fed by VTL's IT-85 integrated amp. My listening room is about 12' x 15' with no room treatment beyond a rug on the floor and curtains over the sliding-glass door. I sometimes feel I'm not hearing as much bass as I should. For instance, the 1st movement of Schubert's Symphony #8 ("Unfinished") begins with the basses (or maybe basses and cellos) playing alone, and it was very striking when I heard the Chicago Symphony play it here in San Diego a few months ago.
So I went home and listened to the same piece on a CD (Bernstein, NY Phil) and yes, the bass at a comfortable listening volume seemed muted compared to the effect in the concert hall.
Vandersteen's website (or maybe the manual for the speakers) recommends Ray Brown's "Soular Energy" album as a good test for bass response. (Brown is a jazz bassist, playing here with piano and drums.) So I put it on just now and indeed, the bass seems more prominent at a slightly-above-normal volume level—in other words, turning up the volume seems to increase bass levels disproportionately more.
But I wouldn't swear to it. It occurs to me that conductors, musicians and recording engineers all make choices about which instruments to feature more prominently, and these may or may not agree with our expectations. Having spent hours trying to eliminate wow and flutter in my turntable that was actually (I think) in the tape the record was mastered from, I've learned that hearing is a complex sense. It's really easy, for me at least, to be persuaded I'm hearing or not hearing something I expected to hear.