I bought an ATI Radeon 8500 64MB. The card served me well for about a year, but I wasn't able to play Medal of Honor: Allied Assault on High Quality with driver default. Then I upgraded to a Nvidia Geforce 4 ti 4600 128MB. This card allowed me to do it plus a little more. I am now waiting for my Sapphire Atlantis Radeon 9600 Pro 128MB to arrive. I chose to upgrade because of its DX9 and AGP8X support and performance wise, the 9600 Pro would work faster than the ti 4600. I think that if you want to play games like HL2, it would be worth upgrading to a 9600 Pro, otherwise just wait for the next generation where I would recommend that you definetly upgrade.
Check
this out.
They are tested on old drivers and arent too reliable.
Check
this out too.
These are tested on newer drivers.
Get what you can out of these, but in a battle between 9600 pro and 5600 ultra, 9600 pro is winner, I researched and chosen before the HL2 bencharks and based on many reviews and many driver versions. Use this information in conjunction with the benchmarks from the sites. Also newer ATI drivers are optimized for 9600 pro and are at times faster than 9500 pro if not faster at all times.