I have a similar setup my cabinets are 70"x20"dx36"w I have 3 buckets (dwc) in both(1 for veg and 1 for flowering) I have a 250w MH and a 250w HPS. It works great, 400w will produce a lot of heat, but if you can keep them cool go for it. This time around I'm trying 2 plants to a bucket. Good luck!