I have a 4x4x7 tent with a 600w and I average 13 oz's per harvest. So I think you could prob pull between 8-9 oz (roughly). But it can vary greatly depending on how you grow (scrog, sog, etc.). I am about to upgrade to a 1k, which is optimal for our size tent.
But also you are growing a lot of kush strains, and kush's are always my lowest yielding plants. Its great bud, but kush's don't yield much. Except that Critical Kush, cause those Critical genes should boost your yield.
Hope that helps, let me know if you have any more questions.