If it's easier to vent and condition the air in the closet, then make that room your flower room and yes the 400 is the same I use and it works very well for a similar size grow. I think you'll like it. Temp and humidity control (and smell control!)is a little more important in flower mode than veggin, so you want to be able to control it as easily as possible. It looks like you've done some research, so dive in and see what happens...ya might wanna try a bag seed run initially and save the good seeds for after you've got all, or most of the kinks worked out. Best of luck!