Back in the day, the cool thing to do was to modify your lower-end Radeon 9800 into a 9800Pro, or at least something like it, by essentially drawing on it with a pencil. Well, here’s a sequel that might actually apply to you.
If you have a certain kind of Geforce 9600 (like this one), all you have to do is flash the BIOS and it rejiggers the card to unlock the unused shader units and the 2 memory units that are deactivated; basically you’re adding 128MB of RAM and some extra hardware pipelines completely by software. It ends up increasing performance by quite a bit. Pretty awesome, huh? Unfortunately, the card it works on is not very common, but it’s good to know these kinds of quickie mods are still viable. Here’s the original guide in Chinese, if you like that kind of thing.