Your rig is 7 years old and all of a sudden, you wish to play the latest games.
Instead of buying a new PC altogether there exists a smarter and cost-effective way of making the best out of your money. Assuming your PC is still 5 years old and has at least a Core 2 Quad CPU with 4 gigs of RAM equipped; you might be able to squeeze a lot from it provided you upgrade the GPU (Graphics Processing Unit.)
AMD or Nvidia?
In the world of graphics cards there is no “special preference.” You need to analyse the current market then you need to decide what you need from your new purchase; it's your hard earned money so you better make it count.
NVidia: If you yearn for faster driver updates, fancy a bit of PhysX and play games that are optimised and sponsored by NVidia. Then the green team is your green signal. Understanding the place of an NVidia card is rather easy. For example GTX660, here the first digit refers to the series. The second digit is the one that truly rates the card. So, basically a good combination of the first two digits is necessary while the third digit is unimportant.
AMD: Want a multi monitor setup? Want to make the best out of your money? Desire RAW power over fancy features? If so then AMD is the one for you. AMD cards share similar numbering schemes as NVidia cards, with only one additional useless digit at the end.
Below here is typically all the homework done for you. This is based on solely what we think is best. Price may be subject to change. Good shopping!