There is an ATI "9 Series" so generally speaking the higher the number the better. so 9600 is better than 9500. See?
Then there is a better series X1K meaning X1000series. Hence the card I recommended is the X1650. Higher the number the better. X1500 is not as good as X1650. See?
Again, generally speaking, what you are looking for in the card is for the specifications to have higher than DirectX9, and OpenGL 2.0 or higher. What also determines if one card is better than another is the mb/gb and bits. So, a 128mb that is 64bit is lower and not as good as a card that is 256mb that is 128bit. Basically, in these departments: The higher the numbers the better!
Left 4 Dead requires a card at least 128mb, so looking for something that is 256mb or 512mb.
Also, please note that some cards require a better power supply, so be sure to look on the box for the system requirements. For example, the card in my new system I'm building requires a power supply of at least 400watts, so I have to buy a power supply that is 400watts or higher, not to mention reliable.
I don't know what all Best buy, or Office Depot will carry in the stores near you. That's why I suggested to use that page I linked you to so you can compare or find a card close to any that are listed on that page. Many cards are very similar(the same really), they are just made by different companys like Saphire, HIS, or Visiontek to name a few.
i.e. A saphire x1650 512mb 128bit card is pretty much the same as a visiontek x1650 512mb 128bit card. They just look different, may or may not have a fan, etc.
Edited by Ferrari, 28 March 2009 - 02:37 PM.