I currently have an Intel (R) Q 35 Express Chipset Family graphics card (256MB) and I would like to replace it with a card that also has an HDMI output. Do I have to choose 256 MB, or can I choose with more capacity?
You can choose with any capacity (obviously reasonable for the performance of the rest of the PC) - the slot you have free on the mainboard (into which you want to put graphics) is important.