For a good experience for starters I would recommend you upgrade your RAM. You should upgrade to 3GB or more if your budget allows. Your CPU is perfectly good for any game you can throw at it including GTA 4.
(I have a similar Intel Core2quad processor paired with a Radeon HD 4850 which runs for about $100 now.). In additon as for a good graphics card you should opt for a Radeon HD 5870 or Nvidia GTX 470 based card if you are looking to buy now and have about $300-$400 to spend. Either of these cards will give you pretty great performance and allow you to play most games at high detail and high resolution with minimum if any lag.
Note: Neither one of these cards are the current 'best' but are both good high performing cards with the slight edge/nod going to the HD 5870 in some situations. GTA4 for PC does not appear to be heavily optimized and tend to not get very high framerates even on pretty high end systems at times but with that card+CPU combo you will be able to play at GREAT detail and relatively smooth framerates.
I recommend 256 MB Nvidia 7900. At least 3 GB ram even more would be better. I have 8 GB of ram.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.