hey... im pretty new to this site, although i have used some small grow chambers just like yours. oddly enough the same dimensions too.. mine was a "band-pass" box for 2-10" speakers, i had a 30W 24" plant gro-lux tube and i had 2 30cfm 80mm. computer case fans mounted to the port holes.... ill be honest, it kept temp perfect @ 74'F but it was hard to manage and it was a hassle because after the first month theyre too tall and the light cant be evenly distributed because of the plant in the way, and you will PROBABLY have to move them because of size (depending on the strain)

just alittle insight from a friend