The creature speakers don't sound as good as you may think.
I have the Logitech Z4 set (2.1), bought on a decent sale.
If I could choose anything, it would be the HK Soundsticks II ($110.92 at Amazon). My brother in law has a set and they sound amazing and look awesome with any of the Macs.
I have the older iSub attached to the Cube along with the pro speakers, and it sounds great.