LEDGardener has build plans for various sizes and strips, for a 4x4 his plans only call for 8 of the strips you want to use for about 80PPF per ft/2 at 500W.
10 strips at 600W(ish) will give you around 1400-1500PPF ( around 90PPF per ft/2) but they will run hotter than double the strips at less power.
THIS THREAD is great for finding deals on LEDS, drivers etc at Arrow Electronics. They have times where seemingly random led strips and drivers are available at very heavily reduced prices.
@MidnightSun72 built
TWO 600W FIXTURES using the same led's (same diodes, different strips) you plan to use, for a total parts cost of $250. If you can wait around for the sporadic price reductions it's well worth it.
ALSO THIS THREAD posts regular deals and specials on Amazon lights and other stuff. Some bargains in there though you will need to be fluent in decoding Chinese marketing spiels.