The composition of the case shouldn't really affect anything. But the design can, you should get one that has good ventilation and lots of fan slots to keep your system cool. An expansion slot is the PCI and AGP ports. AGP graphics cards are the most abudent. The kind of graphics card you want depends on how much you can spend. If you can $300+, you can get top of the line stuff like ATI Radeon X800 and Nvidia GeForce 6800. Each of those cards come in 3 levels, low, medium and high. But for now a Radeon 9600 or 9800 Pro or XT (K'dash, you're help is required here) should do the trick and those are cheaper than the ones mentioned earlier. Go to www.newegg.com to see a selection of cards in your price range, they are a very good site and have very good prices.