worth it to add co2 to my box?

Would it make much difference to add a co2 system to my flower box that only uses a 400 hps. Is co2 more of a benefit to larger wattage setups? I don't want to spend 500+ if it wont make much difference.

try the diy version of co2, its far cheaper. i dont fully know the facts oof co2

How big is your box? if its small enough get a 5 gallon bucket with a lid that seals, and some air hose and try yeast method. It's real cheap and easy.

I've read all the DIY co2 setups, and while they add co2, I don't think its anywhere near the recommended 1500ppm. If I do it, I will do it the right way with a tank, valve, and controller. My box is only 3x3x4, but I will be expanding this summer.

in an area that small i would imagine 1500 ppm would be pretty easy to achieve if its sealed....so in doing all of your research i assume you know how expensive a tank system can be? are you going to have an automated controller? or just the meter hanging somewhere? i dont know why but the controllers and even just the meters are ridiculously expensive. I was going to do co2 with my room but i just couldnt afford it this time around. for a room that small have you seen the co2 boost system?

The system is about 500. 100 for cap reg., 110 for 20lb tank, and 280 for co2 controller (on at 1300 off at 1500). I can get it filled locally for $15. Should last a long ass time with my space. I know if I want bigger/better buds I should upgrade to a 1k bulb but its just not an option right now.
So the real question is regardless of method/cost will adding proper amounts of co2 to plants grown under only 400 Watts significantly increase yeild/quality?

yes it would...I'm sure you already know but 95f is the best temp while your co2 is running. Good luck man. I'm subbed so if you wouldn't mind letting me know how it does for you I'd appreciate it. I was going to incorporate co2 into my system but couldn't afford it this time around.