Connecting 5.1 speakers to an iMac

New to Macs, bought a Mac book pro last month and now I want to swap my main PC for an imac.

I already have a decent set of 5.1 speakers though so i was wondering how I go about connecting these up to an imac?

I also have a decent amp with 2 Co-Axial, 3 Optical inputs so could these be used? The optical are the toslink type.

Any help will be much appreciated.

Thanks

Ricky55

I think is called the Griffen Firewave or something. This question has been asked so many times. Try a seach through the forums here.
And welcome to the forums!