Altersys

Hello, I apologize if this has been answered before. I am in the market for an S4 but need to know a few things about it that only an owner could answer. Right now I only have one question: what is the largest diameter speaker that will fit in the front door of the S4 and what is the available mounting depth?

Does there appear to be a good deal of steel available around the speaker cutout such that a larger cutout could be machined in order to incorporate a larger speaker?

thanks in advance,
-Alt