Well you could get more with the amount of cash you have but i'd still recomend the Altec Lansing MX5021 2:1 Speaker System:
http://www.alteclansing.com/product_details_MX5021_OOS.asp
They seem to be being replaced by the VS4221 System which is probably just as good so if you can check em out'
Or if you wanna be posh (you've got enough money) you could go for Bose Companion 3's (another 2:1 system) - they would match your powerbook! Although they sound good i prefer the MX5021's so much i've got em' on my desk now pumping U2. They are much more powerful sounding than the Companion 3's
Check out the companion 3's here:
http://www.bose.co.uk/home_audio/multimedia_systems/companion3/
I seriously reccomend going and listening to any speakers b4 u buy em tho...
Hope This Helps - Joe.