how many hps for 7x8 flower room?

so here's one for ya... i recently redid my garden (moved locations and expanded) and switched from soil to hydroponics (you can only dump so much soil on your neighbors porch before they get really pissed).. i have a 2x5x5 clone/mother room with 6-4 foot cool flourescents.. my veg room is 5x6x7 with 4 sunleaves satellite iv flourescents.. my flower room will roughly be 7x8x7.. once its actually completed ill post pics.. but its all covered in black and white poly.. nicely sectioned off.. air tight... one 400 cfm (roughly) in each the veg and what will be the flower room... plus a 16 inch air king fan in both.. a can 50 with HO 6inch fan..... will have 2 ebb and grow systems (one for each cycle obviously)... its a really nice half way done set up.. should only take a week or so to finish.. right now tho i have some soil plants that i started flowering on the veg side.. they are under bloom bulbs.. i mean.. i spent almost 5 stacks already.. didnt have enough for the second ebb and grow or more flowering lights.. so once i have another 3 stacks or so ill finish it out.. basically i have one room set up and need more money for a second ebb and grow and lights before i can have it all up and running.. my question is this.. think 6-600 watt hps bulbs on electronic ballasts will be "too much lighting"?? using the 50watt/foot i only need 2800 watts.. but.. i really want to cover the garden well.. and i wont go with 1000 watt.. too inefficent..

2 600's or 2 1k's

2 600's would only put 3600 lumens sq/ft.. and the 1000's are just not worth it.. i'd get 3 600s before 2 1000s.. everything i have read says 5000 lumens sq/ft or more tho... i havent used HPS lights so i dont know how well they work compared to the satellites i use now.. i've even considered just getting more satellites and using them.. the plants i am growing are about 4 feet tall and i want good yield all the way down... so will only 2/3 lights really do the job??