Sun Systems T5 HO, 4 bulb setup. Seen 3 of them do some pretty good stuff. Takes a longer and yeah, needs to be really really close, but they are seriously cool. A 400 watt HPS produces SIGNIFICENTLY more heat. But it also produces more growth too. I dont think anyone will argue that T5 will out perform an HPS. However for vegging and clones they can be great!