Sound card for acer aspire 5600

I have an acer aspire 5600 laptop and the sound is very quiet. I've been using portable speakers but they break very quickly even though i'm very careful with them!
Can I get a sound card that will pump out at least 6 watts and produce a much better sound that's in here now? I'm an instrumental teacher and use alot of recording and music programmes in the lessons. Do you have any ideas?
I have the same problem but, in my case I don't have the correct drivers so I cannot hear anything in my lap. could you please help me to find the driver?