It depends on how fast you want the printer to be.

I built one with 9 BLB 13w integrally ballasted BLB compact flourescent light sources, able to handle a 11x14 contact frame, that prints cyanotypes in 30-60 minutes, for under $80.

I would stick with basic 2 tube ballasts, and not fret the potential for variation in output between three of them unless it proves to be a problem.