Not sure what kind of cutouts you have, but if they're like mine I replaced them a couple of years ago, see http://www.airforums.com/forums/f450...ent-38596.html
. There are also photos of how I removed the speaker covers. You can see a couple of different options in replies from other members too.
Sony apparently no longer sells the XS-R1342 that I used, but I have seen XS-R1343 that looks about the same but blue inside instead of red. Any good 5¼ inch speaker will be a perfect replacement.
A subwoofer is still in the future for me.