I assume the original 'speaker' would be the central one under the dash.

Making a pair of solid, nicely made kick panels for your speakers isn't too difficult to take on (there are many articles and pictures online) and can look very neat and tidy. Will easily mount a 6" speaker and you may as well put a split in there while youre being handy.

Very good place to mount for sound quality. And no irreversible changes and cuts to trim either.