0.5m and light

I bought a Lighthouse Max Growtent 0.5x1x1.8m as I've got limited space.

The manufacturer suggest a 250w light but I wasn't that impressed with my first grow compared to 600w in an old setup of 1x1x2 both 1 plant grows although I get the latter was double the power.

Would a 400w light be overkill in the new tent measuring 0.5x1x1.8m or will I be OK with a 4" RVK outtake fan?

use a cool tube and it should be ok , that is a small space that will heat up very quickly if you plan to keep the tent closed most of the time