Still, sensitivity and more importantly max SPL will go up considerably with close to 50 drivers, and 90 looks about right for 2.83v/1m for 45 of them. This may work, but it will require some quite serious amplification - reacing peak at 20w/driver means 900w dissipated for an SPL of 97db at 1 meter. This is still a bit on the low side, and 11db lower than the RD75 at peak power (400w).

I am not writing this of, but dynamic headroom is important. And based on these numbers the savings from going with the cheaper drivers may not outweigh the costs in terms of less headroom and much more work in building the things...