For your needs, as stated clearly in your request, you may just get away with 1 good card. Your choices should range anywhere between GTX260 maxcore55 896MB to HD 5850. I would highly recommend the 5850, if you can get your hands on one. Best performance/value to date. However, if its out of reach, either because of availability or due to limited budget, I would settle for BFG GTX260 Maxcore 55 OC2 896MB (189.00 USD). This card will perform better than the 1G 4870. Also, with a little patience, uppon Nvidia 300 release possibly this December, the 200 series prices will decline even more. To conclude, I would not recommend the 1G 4870, unless they are in crossfire. As for your memory question, the quantity of RAM that the graphics card contains doesn't have a direct impact on software performance, but an indirect impact. Graphics card RAM will only negatively affect performance if there isn't enough to handle what a specific software requires. To explain farther more, with everything else being exactlly equal, a graphics card with 2GB should perform exactly the same as a graphics card with 512MB as long as the software's graphics memory requirements are below 512MB. If the software SETTINGS and RESOLUTION inhancements require more than 512MB of graphics card RAM, the 512MB card will expirence a "bottleneck" or a lag so to say, to the 2GB card. In addition, 2x512 GPUs and a 1G GPU will be equal in the amount of Ram available for graphics, or at lease to my understanding of this concept. My recommendation surley wil satisfy your needs and will not drain you either. I hope I was somewhat of a help and let me know what you think or if you have any questions.
deadcell
1xBFG GTX295 1792MB DDR3