You should still be able to find PCI video cards that are much better then integrated graphics (at least those in $500 computers), assuming the computer has an open PCI slot and enough physical room to fit in the case. Check the power supply wattage in the computer (it should be on a label on the power supply if it is not included in the system specs) against the requirements for the video card.
Best Buy Finder - Searching Canada's computer stores
