I will soon have a 15" MacBook Pro in my possession. Currently, I use an external Creative Extigy in order to have front and rear speakers hooked up to my laptop. The Extigy is not a very good solution, and it doesn't work well with Macs at all. I'm wondering what a cheap, quality solution would be in order to allow me to continue to use all 4 of my speakers with the MacBook Pro. TIA!