while I know you said you only want two plants flowering just cant really see using 96 inch of height in your flower room very effectivly growing large plants with a 400 over them, one exception might be doing a vertical scrog with the light positioned in the middle.
if you did ever decide to grow more you would be very limited in that cabinet with it split vertically and you may want to split it horizontally instead by maintaining the same height, and reducing the width to about 4 ft and the depth to 2 ft you could very well yield more in a smaller cabinet if you ever decided to use more plants in a sog or scrog using clones. and put the flower room in the top portion at around 56 inches tall and the mother clone area in the bottom with a height of around 40 inches.
you might read the link below for some scrog info
Scrog : Advanced Tactics - The evolution of scrog
and you can read alot about dwc at og faq at the link below.
Drugs-Forum - Cannabis cultivation: Overgrow's GrowFAQ
you can make a good bubbler out of coolers they are more sturdy than the cheaper tubs and also maintain reservoir temps better and are easy to make.