I've been running a V-5x for 1.5 yrs. w/VR4 GenIII's & there is no lack of any bass/midbass. When I switched from a Pass to an ARC pre, the bass was even better, although I recall some PC's that choked the bass (along with the soundstage).
I would suggest the standard drill here-spkr. placement, check your AC, clean connections, etc. before swapping out gear.
I would suggest the standard drill here-spkr. placement, check your AC, clean connections, etc. before swapping out gear.