It's pretty funny... I saw the topic and new the question before I even clicked on it.
Yeah, basically Toyota puts in two sets of 6 1/2 inch speakers, plus a set of tweeters, and calls it an eight speaker system. Don't ask me how they get away with it, but yeah.
I forget where I got mine, but you can do a search on google and find the mounts for aftermarket speakers in our cars. You pretty much have to build your own otherwise.