I actually did the same mod a couple weeks ago (didnt cut out the inner grill but removed the cloth material and the piece of foam) and didnt notice a difference.
Taking out the two foam pieces that rest between the driver and grill should allow for better airflow but I think the foam was originally there to provide some sort of damping. So since I took the foam out, I added a small ring of blu-tak on the back of the driver to give it back some damping. Didnt notice a difference after that either
but you guys can give it a try.