Speaker Amplifier for Computer

Hello, after moving to my new house, the old owners of the house left me a few things including 4 speakers. Two of them are 60W speaker and the other two are 30W. My idea is to essentially connect these speakers, which lack amplifiers, directly to my PC. But, obviously, that would not work without an amp. And, frankly, I do not want to have the big box that came with those speakers (That essentially includes a 5 disk cd player as well as casette tape players). 

So, how would I go about finding an amplifier for that setup that works for computers effectively. The benefits I'm looking for is that I can have 4 channel audio, rather than 2. Anyways, thanks!