The subwoofer which comes with the Soundsticks looks like, but is not identical to the iSub.
I had to buy new external speakers and a Griffin iMic in order to be able to use my iSub with my Intel iMac. In retrospect, it might have been easier and better to buy a new subwoofer... but I was annoyed and too stubborn.
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2.2 GHz Intel Core 2 Duo MacBook w/ 1GB RAM, 160 GB HD, OS 10.5.5
2.0 GHz 20" Intel iMac with 1GB Ram, OS 10.5.5, 225 GB HD, 160GB external LaCie FW HD
1.8 GHz 20" iMac G5 with 1 GB Ram, OS 10.4.11, 145 GB HD, 120GB external LaCie FW HD
Airport Extreme + Airport Express, cable broadband