light cooling

Looking to get a new ballast and light set up. First time using electric ballast. I my self prefer magnetic. But hey first time for everything. So which one is the better one, or can someone point me in a even better direction????? APOLLO VS iPOWER?????????

I am wondering what type of fan/brand to use for my 4x8x6.6 tent with two 600w lights in it. The lights have the 6" duct connections but I see so many types of 6" fans and I'm not sure which ones the one I need. I will have the 8" filter fan sitting outside the tent as well as both ballasts so...