I know the GPU is a low-end one, so was thinking of getting a mid-range one and using both GPUs with Crossfire. However, I don't know if my board supports Crossfire. Also, can I use an NVIDIA card instead of an ATI?
The IGP is an Intel GMA X4500. It can't be Cross fired or SLI'd with anything in a hybrid fashion.
The board itself has only one PCIe x16 Slot so you can't have the option of ptting in 2 Nvidia or 2 ATI cards in it. But anyhow the board will support one ATI or Nvidia GPU and that will go a long way for you in the graphics and gaming way if you use a good GPU.