Don't get the Apple Pro Speakers. Get a set with a subwoofer from a company such as Altec Lansing, JBL, or Harmon-Kardon. Yes, I KNOW the APS drivers are Harmon-Kardon, but they still are overpriced, especially since the sound isn't that great.
If I were you, I'd get a set of fibre-channel 5.1 speakers so you can have a good DVD-playing rig as well, unless you already have a good home theater setup.
You're doing fine with regards to what you're buying. Sure, it's more than enough for what you need, but if you want to dabble in home movies or a little gaming, you'll be glad you paid the extra money.