The only way I was able to fix my levels when I had that exact same rig was to go out & pick up an external pre (UA-5).
In hindsight, I think I could have tweaked the dB & dBU settings in the control panel... Its been about 3 months since I sold my VX so I could be thinking of the wrong place, BUT there is a place in the driver where you can select if you're using line or microphone level inputs by adjusting the nominal and max volume.
I only had the card for 6 weeks before I sold it so YMMV.