My C2D mini is hooked up to an Onkyo 604 AV Receiver which in turn is driving 5.1 Magnat speakers. I am using an analog cable for the moment but hopefully I will get it connected with the optical cable I have (I still need to buy a mini-optical adaptor).
I'll ad to the Harmon Kardon Soundsticks list of fans. I got them for a gift and love them. I will never replace them with a different manufacturer's speakers. Well... unless it's Bose because that's my main home system.
And to evan asking about how to do it: get a mini-optical adapter to plug into the Mini (or an iMac) and simply plug it into an optical input on your receiver.
MSRP $600, but got them from Amazon no tax, free shipping and a huge rebate for $400. The best studio monitors you can buy for $400, or for that matter for $1000. I do all my pro work on them.