I was hoping to get some sort of feedback or advice. I have a 900 mhz iBook and recently purchased a 5.1 speaker system. However, the full features of my speaker system have not been used yet. Apparently I need some sort of extrenal sound card. I am not sure what type of sound card to get. I do know that I need to purchase a USB supported external sound card. Is anyone out there using an extrenal sound card that would support my 5.1 surround sound speakers? Any recommendations or advice of where to pick one up. Im concerned with mac support.