Since you're mentioning this combo, I take it you like the sound of both, so there's a good chance it will work sound-wise. I have a VTL pre and had both BAT amps & pre, but just not at the same time. From what I can remember sonically, I think it'll be a good combination.
What's important is the output/input ratio, so guessing VTL will stay around 200 ohms output impedance and BAT has high input impedance, so this combo will work (on paper).
What's important is the output/input ratio, so guessing VTL will stay around 200 ohms output impedance and BAT has high input impedance, so this combo will work (on paper).