[nfj470]

I am going to be getting my first quality headphones soon (akg k550)and I was wondering what soundcard I should get. I have 2 pci-e x16 slots in my pc open, so I can put any kind of card in.
 
I will be using it to listen to music and play games.
 
What would be the best choice for under $100 new or used, or am I better of just saving my money.