The X100B is the "old old" head Vai used. I had one of the reissues and got good sounds out of it. I got rid of it because when you would turn it on for the first time each day it would do a deafening hiss and I got sick of that.
If the right deal popped up for an original Legacy I would give one a shot, knowing that its going to be dark, so crank the presence and treble.