About 320 nights of the year, Saint Vitus Bar -- a 200-capacity venue in Brooklyn -- hosts performances by such bands as Gozu, Witch Taint and Pentagram giving their all for a room of headbanging, concert-shirt-clad fans. When Saint Vitus co-owner/booker David Castillo extrapolates, he figures close to 1,000 bands a year pass though the nearly 10-year-old club. All over the world, up-and-coming as