In discussions with a veteran Audio Physic dealer, he revealed that their designer takes room dimensions very much into account when designing his speakers. Perhaps, it would be wise to consult with your dealer (or the designer) regarding the suitability of the Virgos for the room in which they are now operating. Several previous posts allude to this solution as well.
For what it's worth, I've found that adding a subwoofer in such situations as yours creates more problems than it solves. Attempting to alloy a sub, whose most useful role is to augment the first one or two octaves, to a speaker that is dynamically unsuited to a particular room results in the failure to integrate the bass with the rest of the audible spectrum.