I'm currently using 400w in my 1m². Do you think it's worth switching my bulb to 600w? Or is that too much for 1m²? I'm going to switch to flowering next week.
I used to grow with a 600W HPS in a 1m² tent and the results were fantastic. The only thing you will have to think about is whether your environment can take the additional heat it will kick out, but if you have adequate ventilation and enough headspace to allow for a few more inches between the lamp and the plant then you'll be fine.