kind of the minimum if you want a decent size, the more you add the better, just watch your heat if you use more. i just picked up some cooltubes. hope it works out for you.
yeah, overlapping 600s should cover it nicely, 7k lumens per sq foot (estimated) on the flower side (hps assumed) and close to 5k lumens per sq ft on the veg (estimated) cant wait to see the finished product.