I think you'd need to check out first if your Power Supply can handle a powerful Graphics Card. Since your PC only has a 300Watt power supply.
I say, you could call Acer and ask them if the computer could handle a better video card. Also, check if upgrading you video card would nullify your Warranty, if it is still under warranty.
I think the reason why your PC is slow in processing graphics is because you have an integrated GPU in your motherboard. Which is pretty weak.
I say, you'd have better performance with a 512 MB ATI 38XX card or Nvidia 8800 installed in your PC at the very least. I also heavily reccomend that you buy a "Palit" video card. Their ATI 3850 is cheaper than any of their competitors that uses the same chip.
