Well I think its like 2500 lumen's Per Sq. Ft. So do the math lol. I hate numbers Sorry.

As for the Lights are you just going to solely use the 400whps for the whole grow? You can use it as your base light and buy some daylight CFL's for Vegging and Soft White's when flowering plus you have your 400whps and that should be sufficient? Just Check around, do some searching, perusing, through the lighting section and you should be Gold! hope this helped.