Does anyone know where a good place to buy cheap graphics card is, that fits the minimum requirements for Civ IV? :)

Local computer stores can generally get you one that will a) work in your computer and b) run the software and games you wish to use.
You can often spend less money buying online at www.newegg.com, www.zipzoomfly.com, and other places. You are then resposible for the upgrade yourself.