If you're planning on running Doom 3 and other games with those type of graphics and resource demands, you should get a fairly decent graphics card with AT LEAST 512MB of RAM and pretty much any processor should be fine for the games now, it's just a matter of how long it will be fine

. A good card for you to start with would be, from the ATI group, a Radeon 9600 or from the NVidia group a GeForce 6600. But those are to start with... Here's a link to a site that will give a better overview of the capabilities of a lot of the cards that are out there right now:
http://graphics.tomshardware.com/gra...705/index.html