hi buckhunter. like i said , i am no expert but my room was 3x4x6 dxwxh so half of yours, and had 400w hps. if i was you i would make that room 4x4 with 600w hps
OR get another400w and put them side by side with two in there OR a light mover.

good luck,hope all goes well.
bigguy.