Monitor selection is a highly personal choice. Two of the more popular brands are Sony and Viewsonic. Really the best advice is to make sure you see an example of the monitor with your own eyes before you buy it. Any of the GS-series Sony monitors are usually safe bets. The Viewsonic professional series is excellent, and the PT-775 would be an outstanding choice.
Value is a very good sound card.
Creative has dominated the sound card business for quite a while, and this card performs well and sounds great. Gamers might also want to take a look at the Diamond Monster MX-300 or one of the other cards based on the Aureal Vortex 2 chipset, as these cards offer some interesting features involving positional sound for certain games. As for desktop speakers, this is one product area where it's getting harder and harder to find good products. The Altec Lansing ACS41 was a good speaker, but the more recent Altec Lansings come with no tweeter. Altec still dominates the desktop speaker market, though.