RAM usage still the same with new GPU?

[Unfocused]

Right now I've got a GeForce 4 MX 440 64MB but plan to change it to a Radeon 9550 (and overclock it to something like R9600 PRO; I heard it's perfect for OC; I know it's not the best GPU but I don't have to much cash to spend on my comp). The question is: for example in HL2, will all those neat dx9 effects take more of my system RAM compared to the amount used with GF4MX440 or will it use only the GPU's memory?

 

[Unfocused]

OK, I'll ask this way: I currently have the above GPU, 2,8Ghz (533FSB) and 256MB RAM. The game is running fine (without the nice effects my GPU cant generate) it lags a bit after loading the game and new levels. The stress test 109fps. So if I'm running it quite comfortably now, when I get the R9550 will I be able to run it comfortably on, lets say, 1024x768 medium? Will the amount of RAM the game uses grow bigger because of the dx9 effects my GPU is going to have to render or doesn't it matter, and the game will be using the same amount of RAM as before.

Yeah, I know I'm asking tough questions

 

[blahblahblah]

Yes, as you bump up graphical details, it will require most system ram. This is because RAM acts as a temporary holding tank for your CPU (and GPU) until your CPU/GPU really needs it. If you enable settings for higher resolution textures, this means you will not have enough RAM to load all the textures need into system memory. So while your GPU is capable of using those high res textures, the rest of your system can't (specifically your RAM). What happens is that load times will increase between levels, and more stuttering will be noticed (especially in wide open areas). So in the end, you will be able to play at a higher visual quality, but you are going to have some annoyances as well.

If you were to buy another stick of 256 MB RAM (roughly 40 USD), that would alievate any bottlenecks caused by RAM.