Led

How many plants would I be able to put underneath a 90 watt led light setup?

No clue man, I can tell you that you would be better off using a HID light instead. I guess if you wanna drop a lotta cash on one of those systems be my guest but I am telling you now that HPS will give you better quality and quantity than LED

yeah I got 400 and 250 but I got a bunch of extra cash to spend and was wondering if one of these cock suckers would be worth it

Nope they won't be worth it, save your money or get some more HID's. If you wanna waste the money that bad you can just send it to me if you would like