Please let us know your budget. I take it you're going to build/upgrade yourself, no pre-built systems, right?
If you can afford it, go with SATA drive(s) & faster memory - 1Gb would be ideal. Are these going to be included in your initial budget?
Would you like a CPU/mobo/ram bundle (like one of these click here), or prefer separate components?
For a start, you could get a SLI/C'fire enabled mobo & a single compatible graphics card, which may be more than sufficient for the games you're presently playing. You could always upgrade when required. And you could spend the money saved on more storage/ram. You'll get better advice about graphics cards from other members like gudgulf - he's the gaming guru (hope this doesn't embarrass him!).
What's your present PSU? You may require a more powerful/compatible one, so that's another cost to factor in. And WinXP, if you don't already have it. G