Hey there ive got a 4x5x2 going right now too, with 2 300 leds. It was going good with 1 when the plants were smaller, but once they got a little bigger they needed their own light. This rose the temperature and i needed to add on a 4 in intake duct fan, it helped but lowered humidity intensely. My 2 36 inch plants are handling the light well but also running out of decent light to plant space...so definitely lst or top etc and you'll have much more room to work with and maybe won't battle some slight light burn like mine. Especially with the bump up to the 600 watt light you'll definitely want to keep the plants as low and flat canopy as possible. Good luck with the new gear. Love the baller dollar dome lol.βοΈ