A mediocre sound card can still deliver decent audio through good speakers, but a crummy set of speakers will never sound good. There are lots of low-cost keyboards out there. Of course, I had to throw in some kind of game controller. Modem I wanted to stick with a name-brand modem. If you're willing to risk an unknown brand, there are lots out there.
External modems are generally easier to set up.
Whatever you do, avoid soft modems, including the US Robotics Winmodem. They work fine for normal Internet browsing, but they can be problematic for gaming. Graphics Card 3D acceleration is here to stay. Most games now require some sort of hardware graphics acceleration and that means using a graphics card. You get 16MB of graphics memory, but no TV out or software bundle.