On my 15" SR MBP (not sure if there is any difference between models) the speakers are the worst of any laptop on my dorm room's hall. All the HPs and Dells blow it away. They don't even go loud enough for a few people to crowd around watching a movie, and they sound terrible.
On the other hand I know a girl here who has a PowerBook with absolutely amazing speakers. She said that they were some sort of custom Bose speakers that she had had installed. Not sure if such options are still available, or if it really matters that much to you, just tossing that out there.