2nd graphics card or soundcard

I have a matx board and have an extra pci-e slot. My question is get another graphics card or get a sound card? I use this to game. I just bought this setup and have a few dollars to spend. My case will not fit a 5850 or I would have bought it. I have 2 1600x1200 monitors and a 1920x1200 monitor. I heard the 5770 can handle the 3 monitors. I play BFBC2, ARMAII, Stalker and L4D. The MSI board has the REALTEK Audio on it. I bought the following:

AMD Phenom IIx4 955
MSI 890gx Matx Board
4gb RAM DDR3
XFX 5770 1GB

Can your power supply handle another graphics card?

Yeah, Corsair 650Watt.

Well for me, I would get the second graphics card 'cause im not really big on sound.