What would be the best ballast for a 600w you could buy? I am looking to upgrade from my 400w hps to 600w. I a magnetic ballast guy but I would be open to digital or electronic ballast. I would want an efficient ballast not the one that would jack up the radio/electronic frequency as I am in an apartment and I want to keep it down low. The most expensive one is not necessarily better. Thanks ahead of time.