I use pretty basic equipment. I don't do cool tubes, I use adjust -A- wing reflectors with lumatek ballasts, all 600 watters. That's in my flower room. I have 6 of them in a 10x8 room with 24 flowering at any given time. It's a perpetual grow. In my veg room I have two 600's and two 400's, a 400 and a 600 of each brand, ipower and Apollo. I also have a "just for me" tent with a lumatek 600 and my wife has a tent with a lumatek 600. And I use two to grow autos with every summer just for fun. I caught a good deal buying a ten pack of em.
I have heard stories of cheap digital ballasts causing RF interference but I have the 4 cheap ballasts mounted about 5 feet away from a tv with a cable box and a little stereo and PERSONALLY I haven't had the slightest bit of interference and neither has my neighbors. The newer models are "supposed" to be RF interference safe. IDK maybe I'm lucky.