You should upgrade only the videocard. The rest are fine for now.
Everything else is fine.
Gpu is a bit under power. Depending on you budget, we could recommend a Good gpu, like ati's newer HD 5xxx gpu's.
Ram, you have plenty of. unless your doing rendering.
cpu, more than enough horse power to run any gpu and game right now. When you do need to upgrade the cpu though, take your current cpu out and put in a core 2 quad Q9550.
One question about your computer. What PSU do you have? (Wattage and model number if possible)